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Sagerman, Denton GregoryHypersonic Experimental Aero-thermal Capability Study Through Multilevel Fidelity Computational Fluid Dynamics
Master of Science (M.S.), University of Dayton, 2017, Aerospace Engineering
As true with all hypersonic flight, the ability to quickly and accurately predict the aero-thermodynamic response of an aircraft in the early design phase is important to not only lower cost, but also to lower the computational and experimental time required to test various parameters. The Mach 6 High Reynolds Number Facility at Wright-Patterson Air Force Base in Dayton, Ohio has been non-operational for the past twenty years, but a recent resurgence in the need for accurate hypersonic test facilities has led to the reactivation of the wind tunnel. With its restoration, new capabilities to assess hypersonic aero-thermodynamic effects on bodies in Mach 6 flow have emerged. Therefore, the objective of this research is to determine if obtaining aero-thermal data from the Mach 6 tunnel using temperature sensitive paint (TSP) is a viable option. Surface pressure and temperature readings, from pressure taps and thermocouples installed on the models, as well as TSP wall temperature distributions will be used for comparison with results from computational fluid dynamics (CFD) analysis codes of differing fidelity levels. The comparisons can then be utilized to gain confidence in the ability of the tunnel to capture the aero-thermal response of complex geometries. Three computational codes were used for numerical comparisons: the Configuration Based Aerodynamics (CBAero) tool set, an inviscid panel code with viscous approximation capabilities, Cart3d coupled with Unstructured Langley Approximate Three-Dimensional Convective Heating (UNLATCH) code to approximate viscous effects from the Euler solution, and finally Fun3d, a fully viscous RANS solver. The three tunnel model geometries that will be used for this research are the Reference Flight System model G (RFSG), a Generic Hypersonic Vehicle (GHV), and the Hypersonic International Flight Research Experimentation Program-Flight 1 (HIFiRE-1) payload geometry.

Committee:

Markus Rumpfkeil, Dr. (Committee Chair); Aaron Altman, Dr. (Committee Member); Jose Camberos, Dr. (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

hypersonics; hypersonic experimental testing; aero-thermal; temperature sensitive paint; CFD; hypersonic CFD; tsp

Pokhrel, SajjanComputational Modeling of A Williams Cross Flow Turbine
Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2017, Renewable and Clean Energy
Hydropower is not only the most used renewable energy source in the United States, but in the world. While it is well known that large hydropower facilities, like the Hoover Dam, provide large amounts of electrical power, there is also a tremendous opportunity for hydroelectric power generation from small scale facilities that has largely been overlooked. The work being presented here studies a new cross flow turbine called the Williams Cross Flow Turbine (WCFT), which was designed to extract electric energy from low head, run-of-the-river, small hydropower sites. To spur the implementation of the WCFT in small hydropower applications, and thus to spur the development of small hydropower, the work here is focused on developing a detailed computational fluid dynamics (CFD) model of the WCFT. The computational model produced as part of this work was developed in the commercial software ANSYS Fluent. This CFD model solves the incompressible Navier-Stokes equations in their three-dimensional, unsteady form including the effects of turbulence, using detailed numerical routines. The multiphase fluid flow of air and liquid water in the turbine is simulated using a volume of fluid technique (VOF). A very detailed geometric representation of the WCFT turbine is imported into ANSYS from the computer aided design software SOLIDWORKS. Using commercial software made the development of this detailed CFD model possible within a Master’s thesis time frame. Coupled to the computational work done here, is some experimental work. Having access to the WCFT experimental facility at Central State University was beneficial to the computational work. A good deal of knowledge about the computer modeling was gained by undertaking a small amount of experimental work. In addition, an experimental result was used to verify the average power predicted by the computational model. This comparison showed a difference of 18.1%, which is deemed reasonable given the complexities of the CFD modeling undertaken. To further verify the computational results, independence of the results on the meshing and time step utilized was demonstrated. The primary computational results presented are plots of turbine power versus shaft rotational speed for twelve and nine bladed WCFTs. These results indicate that a nine bladed WCFT turbine performs better than the currently used twelve bladed, lab-scale WCFT. While these results are specific to the input operating conditions used in the analysis, they indicate the usefulness of the computational tool developed here. Additional results presented for the nine bladed, lab-scale WCFT are field plots of water volume fractions, many types of velocity vector plots, and field plots of the fluid pressure. Histogram plots of some of the interesting quantities are given to show the distribution of certain quantities throughout the turbine.

Committee:

James Menart, Ph.D. (Advisor); Subramania Sritharan, Ph.D. (Committee Member); George Huang, Ph.D. (Committee Member)

Subjects:

Alternative Energy; Energy; Engineering; Environmental Justice; Environmental Law; Environmental Management; Mechanical Engineering

Keywords:

Non Powered Dams; Cross Flow Water Turbine; CFD; Multiphase CFD analysis; k-omega turbulence model

Subramony Anantha, KrishnaEfficacy of New Diagnostic Parameters for Determining Arteriovenous Fistula Functionality: A Numerical Study
MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering
Introduction. The current diagnostic endpoints that are in use to assess the functionality of Arteriovenous Fistula (AVF) are based on either flow or pressure. These parameters, namely vascular access blood flow rate (Qa) and ratio of venous pressure to arterial pressure (VAPR) have been found to provide an inaccurate estimate of AVF functionality in the presence of a venous stenosis. These indices cannot predict the patency of fistula in the future. Recently, two new diagnostic parameters, resistance index (R: ratio of pressure drop across the AVF to flow rate) and pressure drop coefficient (Cp: ratio of pressure drop across the AVF to dynamic pressure) that combine the effect of both pressure and flow, were tested in porcine models. In this study, the effectiveness of these two parameters was studied in a controlled hemodynamic environment on an idealized AVF geometry for different percentage area stenosis (%AS: 0%, 65%, 75%, and 85%) and time-averaged flow rate at proximal artery (Q ¯pa: 600, 1000, and 1600 mL/min). Methods. An idealized AVF geometry was developed using the geometrical data from the AVFs that were created in the porcine models. Computational fluid dynamics (CFD) analyses were performed on the idealized AVF geometry for each of the four stenosis cases and the three Q ¯pa. Both R and Cp were calculated for the twelve cases (four %AS and three Q ¯pa). Results. It was observed that both R and Cp elevated with the increase in %AS for a fixed Q ¯pa. For a fixed AS, the R decreased with the reduction in Q ¯pa, while Cp increased. Conclusion. Reduction of Q ¯pa and an increase in %AS are indicative of a deteriorating AVF functionality, also known as adverse remodeling. The decrease in the value of R with the reduction in Q ¯pa for a fixed %AS can be deduced as a drawback of this parameter. On the other hand, the increase in Cp with the increase in %AS (when Q ¯pa is fixed) and the decrease in Q ¯pa (%AS is fixed) indicates that Cp can detect adverse remodeling in AVFs. Thus, Cp can provide a better prediction of adverse remodeling in AVFs as a result of an increasing stenosis, reducing flow rate, or both.

Committee:

Rupak Banerjee, Ph.D P.E. (Committee Chair); Clarissa Belloni, Ph.D. (Committee Member); Kumar Vemaganti, Ph.D. (Committee Member)

Subjects:

Engineering; Mechanical Engineering

Keywords:

Arteriovenous fistula;Diagnosis;CFD;Dialysis;Numerical analysis;End stage renal disease

Giuliani, James EdwardJet Engine Fan Response to Inlet Distortions Generated by Ingesting Boundary Layer Flow
Doctor of Philosophy, The Ohio State University, 2016, Aero/Astro Engineering
Future civil transport designs may incorporate engines integrated into the body of the aircraft to take advantage of efficiency increases due to weight and drag reduction. Additional increases in engine efficiency are predicted if the inlets ingest the lower momentum boundary layer flow that develops along the surface of the aircraft. Previous studies have shown, however, that the efficiency benefits of Boundary Layer Ingesting (BLI) inlets are very sensitive to the magnitude of fan and duct losses, and blade structural response to the non-uniform flow field that results from a BLI inlet has not been studied in-depth. This project represents an effort to extend the modeling capabilities of TURBO, an existing rotating turbomachinery unsteady analysis code, to include the ability to solve the external and internal flow fields of a BLI inlet. The TURBO code has been a successful tool in evaluating fan response to flow distortions for traditional engine/inlet integrations. Extending TURBO to simulate the external and inlet flow field upstream of the fan will allow accurate pressure distortions that result from BLI inlet configurations to be computed and used to analyze fan aerodynamics and structural response. To validate the modifications for the BLI inlet flow field, an experimental NASA project to study flush-mounted S-duct inlets with large amounts of boundary layer ingestion was modeled. Results for the flow upstream and in the inlet are presented and compared to experimental data for several high Reynolds number flows to validate the modifications to the solver. Once the inlet modifications were validated, a hypothetical compressor fan was connected to the inlet, matching the inlet operating conditions so that the effect on the distortion could be evaluated. Although the total pressure distortion upstream of the fan was symmetrical for this geometry, the pressure rise generated by the fan blades was not, because of the velocity non-uniformity of the distortion. Total pressure profiles at various axial locations are computed to identify the overall distortion pattern, how the distortion evolves through the blade passages and mixes out downstream of the blades, and where any critical performance concerns might be. Stall cells are identified that are stationary in the absolute frame and are fixed to the inlet distortion. Flow paths around the blades are examined to study the stall mechanism. Rather than a static airfoil stall, it is observed that the non-uniform pressure loading promotes a three-dimensional dynamic stall. The stall occurs at a point of rapid incidence angle oscillation, observed when a blade passes through the distortion, and re-attaches when the blade leaves the distortion.

Committee:

Jen-Ping Chen, Ph.D. (Advisor); Jeffrey Bons, Ph.D. (Committee Member); Dunn Mike, Ph.D. (Committee Member); Gaitonde Datta, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

turbomachinery;CFD;inlets

Zhai, QiangA NUMERICAL STUDY OF A HEAT EXCHANGER SYSTEM WITH A BYPASS VALVE
Master of Science, The Ohio State University, 2016, Mechanical Engineering
The primary objective of this research is to study the performance of a heat exchanger system with a bypass valve. At first a simplified double-pipe heat exchanger is considered and a computational fluid dynamic (CFD) code FluentTM 15.0 is used to analyze the heat exchanger performance. The geometry of the double-pipe heat exchanger is scaled down based on the prototypic heat exchanger design provided by Tenneco. Numerical computations are carried out for different inlet conditions provided by Tenneco. The results, including the pressure drop, thermal entrance length, and heat transfer coefficient are benchmarked against correlations available in the literature. Furthermore the performance of the heat exchanger system with a bypass valve is studied. In order to simplify the model, the heat exchanger is modeled using the porous media approach. In addition, the mal-distribution of the flow within the heat exchanger is investigated. The simulations are performed for a range of mass flow rate with both closed and open bypass valve positions. The results are compared with the values obtained using the in-house heat exchanger light tool. The ultimate goal of the thesis is to improve the performance of the overall heat exchanger system to minimize pressure losses and maximize the heat transfer efficiency. This goal could be achieved by optimizing the geometries of the bypass leg to improve the flow uniformity into the heat exchanger and optimizing the flow response dynamics for the open/closed valve positions.

Committee:

Mei Zhuang (Advisor); Xiaodong Sun (Committee Member)

Subjects:

Engineering

Keywords:

CFD simulation; heat exchanger; heat transfer; Fluent

Renjie, KeExperimental and CFD investigations of the fluid flow inside a hydrocyclone separator with an air core
Master of Sciences (Engineering), Case Western Reserve University, 2015, EMC - Mechanical Engineering
Hydrocyclone separators are widely used in various industrial applications in the oil and mining industries to sort, classify and separate solid particles or liquid droplets within liquid suspensions, which are considered to be multi-phase systems. Numerous valuable studies have been conducted in recent years to investigate the flow fields inside hydrocyclones. However, much of the information regarding the performance of cyclones in the literature has limitations, based on in some part on the respectively current-available theoretical models, and much of it cannot be considered as completely applicable to most real-world applications; many of the studies investigated the flow fields within extremely simplified hydraulic designs that are not representative of the complex geometries or large sizes which are typical in industry. Therefore, in this study, the two phase flow system inside the actual hydraulic geometry of a milling circuit hydrocyclone was explored with the aid of both computational and experimental techniques (Particle Image Velocimetry). In this study, the flow field with an air core has been investigated; in essence, the research was a two-phase problem, which caused some challenges on both the computational and experimental sides. The computational modelling was conducted using Star CCM+, a commercial Computational Fluid Dynamics (CFD) software package. Within its built-in mesh generator, a mesh domain containing more than 700,000 unstructured cells was created in a Cartesian coordinate system. In order to improve the numerical calculation accuracy and provide a logical and meaningful comparison with the experimental results, different numerical models were used: the Reynolds Stress Turbulence Model (RSM), Large Eddy Turbulence Model (LES), and the Volume of Fluid multiphase model to handle the air core. The second order discretization scheme was used for both turbulence models. The velocity and pressure contours belonging to various plane sections will be presented and discussed. Additionally, the computational studies also focused on the prediction of the dimensions and shape of the air core. Particle Image Velocimetry (PIV) was used for the experimental measurements. The model hydrocyclone was made of optically clear acrylic. Refractive index matching was achieved using sodium iodide aqueous solution (63.3% NAI by weight) to facilitate PIV measurements. 10 µm silver coated hollow glass spheres were introduced into the flow as tracing particles. Different section planes of hydrocyclone were selected as planes of interest and then were divided into several fields of view (FOV). Two dimensional experimental velocity vector maps were obtained in each of the fields of view. Numerical results are compared to the experimental data. A more physically accurate air volume fraction contour was obtained when the Large Eddy Turbulence model was applied with the Volume of Fluid Multi-phase model, as compared to the RSM model. The shape and diameter of the air core were in good agreement with the experimental results, and the physical time of the air core generation calculated from the simulation approximated to the time scale observed in the experiments.

Committee:

Jaikrishnan Kadambi, Dr. (Committee Chair); Bo Li, Dr. (Committee Member); Vikas Prakash, Dr. (Committee Member); John Furlan, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Hydroyclone separator; PIV; CFD

Rojatkar, PrachiNumerical Analysis of Multi Swirler Aerodynamics
PhD, University of Cincinnati, 2015, Engineering and Applied Science: Mechanical Engineering
Airflow through single- and multi-swirler arrangements for two swirler cup designs with radial–radial counter rotating vanes is computationally investigated using realizable k-ε turbulence model on a grid ranging from 4 million (single swirler) to 36 million points (multi-swirler arrangements). Effect of swirler offset (distance between base wall of confinement and swirler exit plane) for a high swirl number (SN) swirler cup design arranged linearly with 0D, 0.02D and 0.04D offset, where D is swirler exit diameter is analyzed. Flow attaches to the base wall for lower offset conditions. Increasing offset leads to formation of distinct central toroidal recirculation zone (CTRZ) surrounded by jets with presence of recirculation between the adjacent jets and corner recirculation zone (CRZ) at walls. At constant offset, while the mass flow rate through each swirler is essentially the same, the flow field downstream of individual swirlers is quite different in a multi-swirler arrangement. At 0.02D offset a single swirler arrangement has a compact CTRZ with presence of a strong jet and CRZs whereas for the three swirler arrangement fluid entrainment into the central swirler jet leads to flow attachment to the base wall. For a five swirler arrangement the central swirler CTRZ length reduces. A 3x3 arrangement with all swirlers either arranged in a co-swirling or in a co/counter swirling pattern shows presence of a strong jet at each swirl cup along with formation of CTRZs for both arrangements. For co-swirling arrangement the CTRZs are longer in the axial direction with jet extending into the flow with much stronger velocity whereas alternate co/counter arrangement produces more swirler-to-swirler interactions. Changing offset to 0.31D, leads to formation of longer but narrower CTRZ with higher velocity gradient which can lead to better combustion performance. Deflection of the near wall swirler CTRZ is observed for alternate co/counter arrangement due to opposing flow from centermost swirler whereas these CTRZs are more or less symmetric in co swirling arrangement. Effect of flare geometry is studied for low SN swirl cup. Maximum positive axial velocity is comparatively higher while tangential velocity is substantially higher in presence of a flare very close to the swirler exit. For no flare case the tangential velocity variation is mostly due to the outer secondary flow as inner primary flow is rather weak resulting in overall weaker swirl that can adversely affect flame anchoring and combustion performance. Placement of a dummy nozzle at three different placement locations is analyzed. Without a nozzle a strong CTRZ is formed that extends inside the swirler. Placing the dummy nozzle in the region where the primary and secondary path flow merges is found to be the most advantageous as it leads to a strong and compact CTRZ that does not extend inside the swirler geometry. Results presented here show that small changes in a geometric feature of a multi-swirler array can lead to major differences in the resulting flow field. These factors should be carefully considered in design and testing of gas turbine combustors.

Committee:

Milind Jog, Ph.D. (Committee Chair); San-Mou Jeng, Ph.D. (Committee Member); Michael Kazmierczak, Ph.D. (Committee Member); Mark Turner, Sc.D. (Committee Member)

Subjects:

Mechanics

Keywords:

Multi-swirler arrangement;CFD;Numerical analysis;Central toroidal recirculation zone;Confinement;Jet expansion

Ke, XinyouCFD Studies on Mass Transport in Redox Flow Batteries
Master of Sciences (Engineering), Case Western Reserve University, 2014, EMC - Mechanical Engineering
A macroscopic model of flow in a redox flow battery is developed. The model is a layered system comprised of a single passage of a serpentine flow channel and a parallel underlying porous electrode (or porous layer). As the fluid moves away from the entrance of the flow channel, two distinct fully developed flow regime evolve in the channel and the underlying porous layer, respectively. The effects of the inlet volumetric flow rates, permeability of the porous layer, thickness of the flow channel and thickness of the porous layer on the nature of the mass flow in the porous layer are investigated. The results show that, for a Reynolds number of 91.5 with the ideal plug flow inlet condition, the average filtration velocity decreases by a factor of about two as the number of carbon fiber paper layers is increased from 1 to 7. Significantly, reactant flow convection is found to estimate a corresponding maximum current density 403mA cm-2 and 742mA cm-2, which compares favorably with experiments of ~400mA cm-2 and ~750mA cm-2, for a single layer and three layers of the carbon fiber paper.

Committee:

Iwan Alexander (Advisor); Robert Savinell (Advisor); Joseph Prahl (Committee Member); Donald Feke (Committee Member)

Subjects:

Aerospace Engineering; Chemical Engineering; Energy; Mechanical Engineering

Keywords:

Redox flow batteries; Serpentine flow channel; Single passage; CFD; Mass transport; Maximum current density

Underwood, Tyler CarrollPerformance Comparison of Higher-Order Euler Solvers by the Conservation Element and Solution Element Method
Master of Science, The Ohio State University, 2014, Mechanical Engineering
This thesis reports computational efficiency and accuracy of the higher-order space-time Conservation Element and Solution Element (CESE) method for solving the one- and two-dimensional Euler equations. The CESE method is a Computational Fluid Dynamics (CFD) method for time-accurate solution of fluid mechanics equations as well as other linear and nonlinear, first-order, hyperbolic partial differential equations for problems in one, two, and three spatial dimensions. In this thesis, the recently developed, higher-order CESE method by Bilyeu et~al. 2013 will be used. The model equations to be solved are the one- and two-dimensional Euler equations for inviscid compressible flows. Based on the numerical solution of the linear Euler equations, the 4th-order CESE method is more efficient in terms of the CPU time as compared to the original 2nd-order CESE method for achieving the same L2 norm error. The 2nd-order CESE method requires about 20 times more CPU time than the 4th-order method to calculate a solution of the same accuracy. With nonlinear problems, the advantage is not as clear. Though the convergence rate is still much faster for the 4th-order scheme, it uses more CPU time to find the solution unless the accuracy becomes great enough. For the nonlinear Euler equations, similar accuracies can be attained with similar CPU times for different order methods, meaning that the benefit of higher-order methods in these cases is small. For nonlinear problems with shock waves, since the re-weighing function (or the limiter) will be activated due to the solution discontinuity, the solution accuracy is dominated by the solution at the vicinity of the shock wave and the comparison between the 2nd-order method and the 4th-order method is unclear. In general, the 4th-order CESE method is quite robust and it outperforms the original 2nd-order CESE method for solving the linear wave equations.

Committee:

Sheng-Tao John Yu, Ph.D. (Advisor); Mei Zhuang, Ph.D. (Committee Member)

Subjects:

Fluid Dynamics; Mechanical Engineering

Keywords:

CFD; CESE; Conservation Element and Solution Element; Euler Equations; Linear Acoustic Wave; Nonlinear Acoustic Wave; Sod Shock Tube

BHAGAT, ALI ASGAR SALEEMDESIGN AND CHARACTERIZATION OF PLANAR LOW REYNOLDS NUMBER MICROFLUIDIC MIXERS FOR LAB-ON-A-CHIP APPLICATIONS
MS, University of Cincinnati, 2006, Engineering : Electrical Engineering
This work describes the design, fabrication and characterization of two passive microfluidic mixers capable of achieving mixing in less than 7 mm for Reynolds number <0.1. The mixer designs have planar geometry and thus are simpler to fabricate and can be easily integrated with lab-on-a-chip (LOC) technologies. The first design uses diamond-shaped obstructions within the microchannel to break up the flow and recombine into a single laminae to cause mixing. The second design incorporates lamination notches patterned along the channel walls to laminate the flow, thus enhancing mixing. Numerical and experimental studies to determine the effect of the placement of the obstructions and notches inside the microchannel were carried out to optimize the performances of both the mixers. The mixers were then fabricated in polydimethylsiloxane (PDMS) bonded to glass slides and were characterized using fluorescence microscopy. A new interconnect was designed and implemented for easier characterization of devices. The interconnect can be used repeatedly and makes connecting inlets and outlets easier and faster, providing a good seal every time.

Committee:

Dr. Ian Papautsky (Advisor)

Keywords:

Micromixers; LOC; passive mixer; microfluidics; PDMS; CFD-ACE+; fluorescence

Heminger, Michael AlanDynamic Grid Motion in a High-Order Computational Aeroacoustic Solver
Master of Science in Mechanical Engineering, University of Toledo, 2010, Mechanical Engineering

In this work, moving meshes will be employed to solve unsteady computational problems, while maintaining high-order, and high-accuracy. The main problem of interest is that of a plunging piston. The plunging piston problem, first presented in the First Workshop for Computational Aeroacoustics.

Typically, computational aeroacoustics is seperate from aeroelasticity, a field where moving surfaces is integral. This project will join the two field, attempting to resolve propagating waves from a moving boundary. While this particiular problem has been attempted before, it was done using boundary conditions.

This project’s main goal is to bridge the gap between computation fluid dynamic disciplines, creating a general standalone mesh morpher, enabling a new breed of acoustic problems to be solved.

To do this, a highly efficient method of moving the mesh will need to be developed. Since the code uses high-order schemes to resolve the small sound waves, the mesh mover must be methods which keep the grid metrics continuous and smooth.

Committee:

Ray Hixon, Ph.D. (Advisor); Abdollah Afjeh, Ph.D. (Committee Member); Chunhua Sheng, Ph.D. (Committee Member)

Subjects:

Acoustics; Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

cfd; caa; computational fluid dynamics; aeroacoutics; mesh; grid; deformation; morphing; fluid structure interaction; piston

Gifford, Brandon T.Analysis of Heat Transfer in a Thermoacoustic Stove using Computational Fluid Dynamics
Master of Science, The Ohio State University, 2012, Food, Agricultural and Biological Engineering

Thermoacoustic devices have the potential to provide electricity from waste heat to more efficiently use energy resources and to provide new access to electricity for millions of persons around the world. The international SCORE (Stove for Cooking and Refrigeration) research team is studying, designing, testing, and disseminating a biomass cook stove that generates electricity using thermoacoustics. The device captures heat from a small cook stove, uses the thermoacoustic effect to transfer the energy to acoustical sound waves that are captured by a linear alternator and turned into electricity. This study highlights research to characterize and improve the efficiency of heat captured in the SCORE stove.

The SCORE stove prototype, named Demo2, had a measured loss of 45\% in the process of capturing heat from a biomass fire to create an acoustic wave (Riley and Saha, 2010). This research used commercially available Computational Fluid Dynamics software to characterize the physical phenomena occurring inside the Demo2 unit. The simulation model was comprised of all components used in a thermoacoustic device including heat exchangers and regenerator. The thermoacoustic effect itself was not simulated, however. The simulation first derived the steady state temperature and flow fields, given boundary conditions extrapolated from observed experimental data. Secondly, an acoustic wave was induced over the steady state temperature solution to observe the impact on heat transfer. Finally, a simulation was run to calculate pressure transmission loss due to geometry.

Simulations predicted heat capture and transfer from the biomass fire's exhaust gases to the working air inside the unit. The amount of heat captured was low and therefore it is recommended that design of the hot heat exchanger should be altered to boost heat transfer. Results indicate that during stove operation absent of acoustics, radiation is the dominant mode of transferring heat. Surfaces closest in space and parallel to receiving surfaces had the highest heat flux. Simulations modeling acoustics showed convection during all portions of the sound wave to be greater the mode of heat transfer. It is recommended that heat exchanger geometry should be altered to expand the hottest sections of temperature distribution over the hot heat exchanger to improve both radiation at startup and convection during acoustic operation. Conduction in the air should be neglected at all times. Transmission pressure loss simulations for the acoustic wave due to geometry exceed 25%.

Committee:

Dr. Ann Christy, PhD (Advisor); Dr. Scott Shearer, PhD (Committee Member); Dr. Lingying Zhao, PhD (Committee Member)

Subjects:

Acoustics; Agricultural Engineering; Mechanical Engineering

Keywords:

Thermoacoustics; CFD; Heat Transfer; Improved Cookstove;

Yatsco, Michael P.Numerical Analysis and Wind Tunnel Validation of Wind Deflectors for Rooftop Solar Panel Racks
Master of Science in Engineering, Youngstown State University, 2011, Department of Mechanical and Industrial Engineering
Solar power since the past decade has become one of the very promising energy alternatives to the non-renewable forms of energy such as coal and natural gas. Solar panels that harvest solar power do not require the amount of space compared to other forms of renewable energy like wind turbines. In addition, solar panels have virtually an unlimited source of power derived from the sun and it can even be installed on the rooftops of buildings. One problem that arises with the placement of solar panel racks on the rooftops of buildings is occasional high wind loads the racks experience, requiring an efficient and optimized wind management system, sometimes known as wind deflectors. Wind deflectors not only prevent the solar panels from wind loads, but also ensure the safety of civilians and the surrounding property. This thesis employs the combinatorial utilization of experimental wind tunnel tests to validate the computational fluid dynamics (CFD) code embedded in ANSYS Fluent Software for analysis, design, and optimization of the wind deflector. The work in this thesis includes the consideration and detailed analysis of wind loads on the solar panels due to high wind speeds, leading to the design of an optimized wind deflector to prevent such loads. Research study comprehends physical modeling, mathematical modeling, and numerical simulation validated by wind tunnel tests to analyze the wind loads on scaled models. Extensive experimental data and simulation results were thoroughly analyzed and it was concluded that an elliptic-profiled wind deflector with fins positioned before the solar panels can reduce the wind loads by approximately 50%.

Committee:

Yogendra Panta, PhD (Advisor); Ganesh Kudav, PhD (Advisor); Hazel Marie, PhD (Committee Member)

Subjects:

Fluid Dynamics; Mechanical Engineering

Keywords:

CFD; Wind Tunnel; Numerical; Solar Panel Racks

Atkinson, Michael D.Control of Hypersonic High Angle-Of-Attack Re-Entry Flow Using a Semi-Empirical Plasma Actuator Model
Doctor of Philosophy (Ph.D.), University of Dayton, 2012, Aerospace Engineering

The aim of this dissertation was to explore the possibility of using flow control to stabilize re-entry flight at very high angle-of-attack. This was carried out in three steps: 1) study the structure of representative high angle-of-attack re-entry flows; 2) develop a semi-empirical plasma actuator model that can be applied to control high angle-of-attack re-entry flows; 3) application of the plasma actuator model to study the control of representative re-entry flows. The calculations include viscous and thermochemical non-equilibrium effects, and a high-fidelity physical model to resolve complex flow structure.

The contribution of this dissertation was to provide a detailed description of hypersonic viscous flow around blunt-nosed elliptical cone at very high angle-of-attack. High-fidelity, thermochemical non-equilibrium numerical solutions of high angle-of-attack re-entry flows were not published prior to this research, and thus this research can provide a foundation to calculate, analyze, and describe very high angle-of-attack hypersonic re-entry flows.

Paramount to this dissertation was the development of a new phenomenological MHD plasma actuator model. A semi-empirical actuator model was developed by adding source terms to the momentum equation, vibrational energy equation, and total energy equation, employing an exponential decay function based on the formulations of Kalra et al. and Poggie. This new plasma actuator model was extended from Poggie's model to include thermochemical non-equilibrium effects and expanded from Kalra's et al. two-dimensional model to include three-dimensional effects. Development, validation, and calibration of the plasma actuator model was based on a qualitative comparison to the experiment of Kalra et al. on manipulating turbulent shock-wave/bounday layer interaction using plasma actuators. The effect of the plasma actuators on turbulent shock-wave/boundary-layer interaction was simulated numerically and a detailed description of the complex flow structure with and without actuation was provided.

Finally, application of the plasma actuators to control the complex flow structure of high angle-of-attack re-entry flight vehicles was investigated. To the best of the author's knowledge, no prior research on high angle-of-attack re-entry vehicle control using plasma actuators has been published. Lastly, this dissertation serves as a foundation to compute, analyze, and control complex flow generated around re-entry vehicles at high angle-of-attack.

Committee:

José A. Camberos, PhD (Committee Chair); Jonathan Poggie, PhD (Committee Co-Chair); Aaron M. Altman, PhD (Committee Member); Youssef N. Raffoul, PhD (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

Hypersonic, Reentry; CFD; Plasma actuators; Flow Control; High angle of attack

Sander, Zachary HugoHeat Transfer, Fluid Dynamics, and Autoxidation Studies in the Jet Fuel Thermal Oxidation Tester (JFTOT)
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
Modern military aircraft use jet fuel as a coolant before it is burned in the combustor. Prior to combustion, dissolved O2 and other heteroatomic species react with the heated fuel to form insoluble particles and surface deposits that can impair engine performance. For safe aircraft operation, it is important to minimize jet fuel oxidation and resultant surface deposition in critical aircraft components. The Jet Fuel Thermal Oxidation Tester (JFTOT) is a thermal stability test that measures the tendency for fuel to form such deposits and delivers a pass/fail grade for each fuel tested. However, the extent of oxidation and the corresponding deposition occurring in the JFTOT is not fully understood. A JFTOT Model Mark II was modified to include a bulk outlet thermocouple measurement and a downstream oxygen sensor to measure bulk oxygen consumption. Experimental results show a direct relationship between the bulk outlet temperature and JFTOT setpoint temperature with the bulk outlet less than the setpoint temperature. Several fuels were also tested at varying setpoint temperatures with complete oxygen consumption by 320°C and a wide range of oxygen consumption from 10-85% at 260°C. Due to the complex fluid flows in the JFTOT, computational fluid dynamics (CFD) was used to model the heat transfer and fluid flow. A three-dimensional simulation showed considerable recirculation within the JFTOT due to buoyancy effects from gravity and resulted in complex residence time behavior. In addition, CFD simulations performed with a pseudo-detailed chemical kinematic mechanism showed an under prediction in both oxidation and deposition for similar fuels tested experimentally but yielded bulk outlet temperature predictions of less than 2% error. Simulations of deposition were of the right order of magnitude and matched the deposit profile of comparable experimental ellipsometry data.

Committee:

Steven S. Zabarnick, PhD (Committee Co-Chair); Jamie S. Ervin, PhD (Committee Co-Chair); James T. Edwards, PhD (Committee Member)

Subjects:

Aerospace Engineering; Chemical Engineering; Chemistry; Energy; Engineering; Fluid Dynamics; Mechanical Engineering; Petroleum Engineering

Keywords:

JFTOT;CFD; heat transfer; oxidation; autoxidation; deposition; ellipsometry; jet fuel thermal oxidation tester; oxygen consumption; FT; fischer tropsh; hrj; jp-8; jet a-1; thermal stability; fluid mechanics; astm d3241; flir; interferometry; udri

Godoy, Ruben D.Lethal and sub-lethal effects of hydrodynamic forces on animal cell culture
Doctor of Philosophy, The Ohio State University, 2008, Chemical Engineering

Biotechnology-derived protein drugs, usually referred as biologics, represent a significant part of the whole pharmaceutical market. Typically, biologics are produced in genetically modified animal cells, which are regarded by many engineers and practitioners in the pharmaceutical industry as extremely sensitive to hydrodynamic forces. Since during research or normal operation in the biopharmaceutical industry cells are exposed to a range of hydrodynamic forces, this "shear sensitivity" idea often leads to very mild, sub-optimal designing and operating conditions.

To determine the actual levels of hydrodynamic stress capable of affecting the metabolism or viability of a cell line in bioprocessing or analytical devices, a microfluidic contracting-expanding device was developed in our group that exposes cells to controlled, well-defined hydrodynamic forces by means of keeping the flow in laminar conditions. Using this device, changes in cell behavior can be determined as a function of the local energy dissipation rate (EDR). EDR is a scalar value that is intrinsic to any moving fluid, is independent of the flow regime (turbulent/laminar) and accounts for both shear and extensional components of three-dimensional flow. It represents the rate at which work is done on a fluid element or a cell. If laminar flow is maintained, EDR can be reliably calculated using well-established equations for simple geometries or computational fluid dynamics (CFD) software for more complex problems.

The microfluidic device, consisting of a micro-channel bored in a stainless steel sheet in sandwich between two polycarbonate plates, was used in different setups to imitate the environment cells will experience in both bioprocessing and analytical equipment. As a model for analytical devices, it was selected a Fluorescent Activated Cell Sorter (FACS), where cells are forced through a nozzle and interrogated by a laser beam. This instrument was mimicked by passing the cells once through the microfluidic device; on the other hand, as a model for bioprocessing equipment, the hydrodynamic forces a cell experiences in a bioreactor were simulated by recirculating the cells through the microchannel, in an intent to reproduce the cyclic passage of the cells through the high EDR zone around the impeller to zones of relative low EDR intensity away from it. Several cell lines of industrial, research and medical interest were tested using the just described methodology. For single passage, in every case the elicited response was mainly an increase of cell necrosis with larger EDR while only a small fraction of cells became apoptotic when exposed to the highest levels of EDR tested. Changes in medium composition or genetic modifications did not affect this behavior.

The response to repeated, chronic exposure to moderate levels of EDR was case-specific. A research CHO cell line (CHO6E6) stopped growing at the lowest levels of chronic EDR evaluated (2.9x105 W·m-3) and started dying when the EDR intensity was increased. On the other hand, the growth curve of a GS-CHO industrial cell line that produces a fully human antibody was not affected at all even at the highest EDR tested (6.5x106 W·m-3), although the glycosylation pattern of the antibody suffered modifications. Single passage results for both cell lines showed a very similar behavior to previously tested cell lines. Interestingly, results showed that at least some medical cell lines (THP1) might have an EDR threshold lower than industrial or research cell lines (i.e., more "shear" sensitive), which suggest a possible selection of the tougher individuals after continuous manipulation. This conclusion seems to be also supported by the chronic exposure of the industrial GS-CHO cell line at the highest chronic EDR tested. If this is the case, the microfluidic device could even become a tool for selection of stronger clones in the pharmaceutical industry.

Committee:

Jeffrey Chalmers, PhD (Advisor); Kurt Koelling, PhD (Committee Member); Andre Palmer, PhD (Committee Member)

Subjects:

Chemical Engineering; Pharmaceuticals

Keywords:

Animal Cell; Culture; CHO; THP1; Cell Death; Shear; Sensitivity; Stress; Hydrodynamic; Force; Antibody; Monoclonal; Glycosylation; Apoptosis; Necrosis; CFD; Fluent; Flow Cytometry

Bruzzese, John ReedDevelopment Of An Electric Discharge Oxygen-Iodine Laser And Modelling Of Low-Temperature M=4 Flow Deceleration By Magnetohydrodynamic Interaction
Master of Science, The Ohio State University, 2008, Aeronautical and Astronautical Engineering
The present work addresses performance optimization of a small-scale, electric discharge excited, gasdynamic oxygen iodine laser (DOIL). For this, (i) nitric oxide has been added to the laser mixture, and (ii) iodine vapor was dissociated in an auxiliary electric discharge prior to its injection into the laser flow. The addition of NO has a significant effect on the laser performance, increasing small signal gain in the supersonic laser cavity from 0.05 %/cm to 0.08 %/cm. On the other hand, although large iodine dissociation fractions in the laser cavity have been achieved using an auxiliary discharge (up to 50%), only modest increase in gain was detected. The DOIL laser apparatus has been scaled up, with the main electric discharge volume increased by a factor of four and the flow rate through the laser doubled. The scaled-up laser has been tested using a nanosecond pulser / DC sustainer discharge or a capacitively coupled radio frequency discharge (CCRF) sustained at powers up to 2.7 kW and 4.5 kW, respectively. In both these cases, single-delta oxygen yield of up to 3-4% has been measured. Small signal gain up to 0.116 %/cm has been measured in the laser cavity while using the CCRF discharge to generate singlet delta oxygen. Numerical modeling of magnetohydrodynamic deceleration of a low-temperature M=4 flow was conducted using a three-dimensional compressible Navier-Stokes flow code. The results are in good agreement with recent experiments conducted at Ohio State, where flow deceleration by up to 2% has been demonstrated.

Committee:

Igor Adamovich (Advisor)

Subjects:

Engineering

Keywords:

DOIL; e-COIL; MHD; Magnetohydrodynamic; CFD; Laser; singlet delta oxygen;

Modekurti, ArvindNumerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections
MS, University of Cincinnati, 2017, Engineering and Applied Science: Mechanical Engineering
The periodically fully-developed laminar flow and heat transfer for shear-thinning non-Newtonian fluids flowing through helically twisted ducts of elliptical cross-section have been numerically simulated using a finite-volume CFD solver. The geometry of the twisted duct is defined using the parameters aspect ratio, α and twist ratio, y. The present study considers duct geometries with the twist ratio, y = 3, 4.5, 6, ∞ and aspect ratio, α = 0.5,0.7,1. The shear-thinning non-Newtonian fluids chosen for the analysis comprise of three grades of aqueous solutions of Carboxymethylcellulose (CMC) which are CMC 7H3SF (High Grade), CMC 7M8SF (Medium Grade) and CMC 7LFPH (Low Grade). The properties of the non-Newtonian fluids are assumed to be temperature independent and their constant property values at 60°C are considered in the present study. A constant wall temperature boundary condition is assumed to perform the heat transfer simulations. The asymptotic modified power-law model has been used to describe the shear-thinning behavior of non-Newtonian fluids under consideration. The zero shear rate viscosity, μ0 which is known a priori for each shear-thinning fluid is used as a reference viscosity to define the flow Reynolds number, Re. The range of Reynolds number, Re within which the thermal and hydraulic performance parameters for various CMC polymers are evaluated is 2.20 = Re = 340 for CMC 7LFPH, 2.20 = Re = 74.2 for CMC 7M8SF and 2.20 = Re = 31.1 for CMC 7H3SF. The numerical analysis shows the influence of geometric parameters as well as the properties of non-Newtonian fluids on Fanning friction factor, f and Nusselt number, Nu. The enhancement in Nusselt number, Nu and decrease in friction factor, f with increasing shear-thinning nature of non-Newtonian fluids is observed in straight ducts with y = ∞. The enhancement in Nusselt number, Nu and the corresponding pressure drop penalty in a twisted duct with respect to a straight duct flow due to the additional presence of secondary swirl flows are expressed as Nu / Nuy=∞ and f / fy=∞ . The value of Nu / Nuy=∞ in the high Reynolds number range increases with a decrease in aspect ratio, α and decrease in twist ratio, y. The enhancement in Nu for a twisted duct is negligible in the low Reynolds number range and begins to rapidly increase at higher Reynolds number due to the onset of strong secondary swirl flows which improve the fluid mixing within the duct cross-section. In the present study, the enhancement in Nusselt number, Nu / Nuy=∞ and the corresponding increase in friction factor, f / fy=∞ was observed to be the highest in the case of a severely twisted duct with twist ratio, y = 3 and a low ellipse aspect ratio, α = 0.5 where the intensity of the secondary swirl flows induced by the curved walls of the twisted duct is the highest.

Committee:

Milind Jog, Ph.D. (Committee Chair); Je-Hyeong Bahk, Ph.D. (Committee Member); Raj Manglik, Ph.D. (Committee Member)

Subjects:

Mechanical Engineering; Mechanics

Keywords:

Heat Transfer Enhancement;Twisted Elliptical Ducts;Non-Newtonian fluids;Friction Factor;Nusselt number;CFD

Thanapisudwong, ThatchaiThe Impact of Raceway Mixing and Light Penetration on Algal Growth
Master of Science (MS), Ohio University, 2016, Civil Engineering (Engineering and Technology)
Raceway ponds for microalgae are broadly used in cultivating microalgae for high production because of their effectiveness and cost savings. One of the challenging factors of microalgae growth is how to optimize the impact of mixing during cultivation. The effects of light characteristics, LED, and fluorescence, are also significant for growing microalgae. Mixing paddlewheel speeds were investigated using speeds at 11 rpm, 13 rpm, and 15 rpm. Maximum algae concentrations and growth rates were higher with higher rpm. Shear calculations showed that these mixing rates were not high enough to injure cells. Maximum velocities in raceways varied from 16.5 to 41.8 cm/s, adequate for mixing. LED lights were more effective than fluorescent likely due to higher intensity and better radiation spectra. Growth nearly stopped after six days due to high turbidities that greatly diminished light penetration. A CFD model matched measured velocities well and showed eddy problems were more severe at lower mixing rates.

Committee:

Guy Riefler, R. (Advisor); Shad Sargand (Committee Chair); Sarah Davis (Committee Member); Ben Sperry (Committee Member)

Subjects:

Civil Engineering

Keywords:

Raceway pond; Microalgae; Paddle Wheel; Light Intensity; Growth Rate; CFD

Clark, AdamPredicting the Crosswind Performance of High Bypass Ratio Turbofan Engine Inlets
Doctor of Philosophy, The Ohio State University, 2016, Aero/Astro Engineering
Takeoffs in crosswind conditions are a common occurrence in flight operations around the world, and flow separation from the inlet of a jet engine at this condition can lead to fan stall, surge, or aeromechanical excitation. The ability to predict flow separation and reattachment is critical to the design of a performance-optimized inlet and to reduce the risk of crosswind performance shortfalls during engine certification. This dissertation shows the derivation of an aerodynamic loading coefficient referred to as the Reattachment Parameter (RP). Analysis of wind tunnel test data for five different inlet designs at five different crosswind speeds show that inlet reattachment occurs when a single, critical value of RP is reached. A process for predicting flow reattachment is developed that relies solely on static pressure distributions from inviscid CFD and the RP coefficient. Validation of predictions from this process were accomplished with wind tunnel testing of two new ultra-high bypass ratio (UHBR) inlets and full-scale testing of a new conventional-length inlet on a modern turbofan engine. The average error in the reattachment predictions of the two UHBR inlets was 1.4% of peak flow and 4.3% of peak flow for the full-scale engine test. Reattachment predictions with the RP process were consistently found to be more accurate than those from RANS CFD. A second key advantage of the RP process is that, by leveraging inviscid CFD, a reattachment prediction can be made with about 1/100,000th the computational cost of a RANS prediction, which provides a tremendous advantage during inlet design work. Results from the RP process suggested that spinner size and shape may affect the crosswind performance of an inlet, so the effect of replacing a standard wind tunnel spinner with one that is larger and more representative of flight hardware was examined. Analysis with the RP process predicted reattachment with the larger spinner would occur 10.6% of peak flow earlier than the smaller spinner. Wind tunnel testing of both spinners showed a 9.5% of peak flow earlier reattachment for the larger spinner. Finally, the ability of the RP coefficient to quantify the circumferential distribution of aerodynamic loading is used to develop a novel design strategy referred to as `load balancing'. Knowledge of the circumferential locations which experience the highest aerodynamic loading allows a designer to alter the inlet geometry in order to achieve a more uniform load distribution. This process provides inlet designers with a unique ability to improve the crosswind performance of an inlet without negatively affecting other important performance characteristics.

Committee:

Jen-Ping Chen (Advisor); Jeffrey Bons (Committee Member); Michael Dunn (Committee Member); Richard Freuler (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

CFD; jet engine; inlet; crosswind; separation; reattachment; distortion; IDC; RANS; Euler; inviscid; loading parameter; pressure gradient; aerodynamics; nacelle; angle of attack; separation bubble; aerodynamic loading; pressure coefficient; hysteresis

Bourke, Jason MichaelImplications of Airflow Dynamics and Soft-Tissue Reconstructions for the Heat Exchange Potential of Dinosaur Nasal Passages
Doctor of Philosophy (PhD), Ohio University, 2015, Biological Sciences (Arts and Sciences)
This study seeks to restore the internal anatomy within the nasal passages of dinosaurs via the use of comparative anatomical methods along with computational fluid dynamic simulations. Nasal airway descriptions and airflow simulations are described for extant birds, crocodylians, and lizards. These descriptions served as a baseline for airflow within the nasal passages of diapsids. The presence of shared airflow and soft-tissue properties found in the nasal passages of extant diapsids, were used to restore soft tissues within the airways of dinosaurs under the assumption that biologically unfeasible airflow patterns (e.g., lack of air movement in olfactory recess) can serve as signals for missing soft tissues. This methodology was tested on several dinosaur taxa. Restored airways in some taxa revealed the potential presence and likely shape of nasal turbinates. Heat transfer efficiency was tested in two dinosaur species with elaborated nasal passages. Results of that analysis revealed that dinosaur noses were efficient heat exchangers that likely played an integral role in maintaining cephalic thermoregulation. Brain cooling via nasal expansion appears to have been necessary for dinosaurs to have achieved their immense body sizes without overheating their brains.

Committee:

Lawrence Witmer, PhD (Advisor)

Subjects:

Anatomy and Physiology; Animal Sciences; Biology; Biomechanics; Fluid Dynamics; Paleontology; Scientific Imaging; Zoology

Keywords:

dinosaurs; computational fluid dynamics; CFD; anatomy; reptiles; birds; biomechanics; turbinates; brain cooling; thermoregulation; fluid dynamics; Stegoceras; Euoplocephalus; Panoplosaurus; bony-bounded; airway; nasal passage; nasal cavity

Miller, Samuel C.Fluid-Structure Interaction of a Variable Camber Compliant Wing
Master of Science (M.S.), University of Dayton, 2015, Aerospace Engineering
This thesis presents results from loosely-coupled fluid-structure interaction (FSI) simulations of a flexible wing which used FUN3D to compute the aerodynamic flow-fields and Abaqus to calculate the structural deformations. NASA Langley also provides a general 3D algorithm to interpolate between dissimilar meshes which is used here to map pressures and displacements between the aerodynamic and structural codes. This method is applied to the AFRL - developed “Variable Camber Compliant Wing” (VCCW), which is an adaptable wing designed to target airfoil shapes between a NACA 2410 and 8410. The VCCW was tested in the Vertical Wind Tunnel facility at Wright-Patterson Air Force Base, which provided experimental data in the form of static pressure tap data, digital image correlation, and oil flow visualization. The combined solutions from Abaqus, FUN3D, and mesh interpolation solvers created FSI results that were similar in trend to the experiment, but consistently under-predicted the deformations of the VCCW, due to the differences between the experiment and simulation, including the choice of material models and the assumption of ideal conditions. This thesis has been cleared by the Wright-Patterson AFB Public Affairs Office, case number 88ABW-2015-1502. This provides proof of public release, distribution unlimited.

Committee:

Markus Rumpfkeil, Phd (Advisor); James Joo, Phd (Committee Member); Jose Camberos, Phd (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

CFD; FSI; Computational Fluid Dynamics; Fluid-Structure Interaction;Flexible Wings; Compliant Mechanism; Loosely-Coupled; FUN3D; Abaqus; Python

Ickes, JacobImproved Helicopter Rotor Performance Prediction through Loose and Tight CFD/CSD Coupling
Master of Science, University of Toledo, 2014, Mechanical Engineering
Helicopters and other Vertical Take-Off or Landing (VTOL) vehicles exhibit an interesting combination of structural dynamic and aerodynamic phenomena which together drive the rotor performance. The combination of factors involved make simulating the rotor a challenging and multidisciplinary effort, and one which is still an active area of interest in the industry because of the money and time it could save during design. Modern tools allow the prediction of rotorcraft physics from first principles. Analysis of the rotor system with this level of accuracy provides the understanding necessary to improve its performance. There has historically been a divide between the comprehensive codes which perform aeroelastic rotor simulations using simplified aerodynamic models, and the very computationally intensive Navier-Stokes Computational Fluid Dynamics (CFD) solvers. As computer resources become more available, efforts have been made to replace the simplified aerodynamics of the comprehensive codes with the more accurate results from a CFD code. The objective of this work is to perform aeroelastic rotorcraft analysis using first-principles simulations for both fluids and structural predictions using tools available at the University of Toledo. Two separate codes are coupled together in both loose coupling (data exchange on a periodic interval) and tight coupling (data exchange each time step) schemes. To allow the coupling to be carried out in a reliable and efficient way, a Fluid-Structure Interaction code was developed which automatically performs primary functions of loose and tight coupling procedures. Flow phenomena such as transonics, dynamic stall, locally reversed flow on a blade, and Blade-Vortex Interaction (BVI) were simulated in this work. Results of the analysis show aerodynamic load improvement due to the inclusion of the CFD-based airloads in the structural dynamics analysis of the Computational Structural Dynamics (CSD) code. Improvements came in the form of improved peak/trough magnitude prediction, better phase prediction of these locations, and a predicted signal with a frequency content more like the flight test data than the CSD code acting alone. Additionally, a tight coupling analysis was performed as a demonstration of the capability and unique aspects of such an analysis. This work shows that away from the center of the flight envelope, the aerodynamic modeling of the CSD code can be replaced with a more accurate set of predictions from a CFD code with an improvement in the aerodynamic results. The better predictions come at substantially increased computational costs between 1,000 and 10,000 processor-hours.

Committee:

Chunhua Sheng, Ph.D. (Advisor); Abdeh Afjeh, Ph.D. (Committee Member); Ray Hixon, Ph.D. (Committee Member); Glenn Lipscomb, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

Computational Fluid Dynamics; Computational Structural Dynamics; CFD; CSD; Helicopter; Rotor; Coupling; UH-60A; Rotorcraft; Aerodynamics

Byrd, Alex W.Fluid-Structure Interaction Simulations of a Flapping Wing Micro Air Vehicle
Master of Science in Engineering (MSEgr), Wright State University, 2014, Mechanical Engineering
Interest in micro air vehicles (MAVs) for reconnaissance and surveillance has grown steadily in the last decade. Prototypes are being developed and built with a variety of capabilities, such as the ability to hover and glide. However, the design of these vehicles is hindered by the lack of understanding of the underlying physics; therefore, the design process for MAVs has relied mostly on trial-and-error based production. Fluid-Structure Interaction (FSI) techniques can be used to improve upon the results found in traditional computational fluid dynamics (CFD) simulations. In this thesis, a verification of FSI is first completed, followed by FSI MAV simulations looking at different prescribed amplitudes and flapping frequencies. Finally, a qualitative comparison is made to high speed footage of an MAV. While the results show there are still model improvements that can be made, this thesis hopes to be a stepping stone for future analyses for FSI MAV simulations.

Committee:

George Huang, Ph.D. (Advisor); Philip Beran, Ph.D. (Committee Member); Joseph Shang, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

Micro air vehicles; Fluid Structure Interaction; Computational Fluid Dynamics; MAV; FSI; CFD

Leger, Timothy JamesDevelopment of an Unsteady Aeroelastic Solver for the Analysis of Modern Turbomachinery Designs
Doctor of Philosophy (PhD), Wright State University, 2010, Engineering PhD

Developers of aircraft gas turbine engines continually strive for greater efficiency and higher thrust-to-weight ratio designs. To meet these goals, advanced designs generally feature thin, low aspect airfoils, which offer increased performance but are highly susceptible to flow-induced vibrations. As a result, High Cycle Fatigue (HCF) has become a universal problem throughout the gas turbine industry and unsteady aeroelastic computational models are needed to predict and prevent these problems in modern turbomachinery designs. This research presents the development of a 3D unsteady aeroelastic solver for turbomachinery applications. To accomplish this, a well established turbomachinery Computational Fluid Dynamics (CFD) code called Corsair is loosely coupled to the commercial Computational Structural Solver (CSD) Ansys® through the use of a Fluid Structure Interaction (FSI) module.

Significant modifications are made to Corsair to handle the integration of the FSI module and improve overall performance. To properly account for fluid grid deformations dictated by the FSI module, temporal based coordinate transformation metrics are incorporated into Corsair. Wall functions with user specified surface roughness are also added to reduce fluid grid density requirements near solid surfaces. To increase overall performance and ease of future modifications to the source code, Corsair is rewritten in Fortran 90 with an emphasis on reducing memory usage and improving source code readability and structure. As part of this effort, the shared memory data structure of Corsair is replaced with a distributed model. Domain decomposition of individual grids in the radial direction is also incorporated into Corsair for additional parallelization, along with a utility to automate this process in an optimal manner based on user input. This additional parallelization helps offset the inability to use the fine grain mp-threads parallelization in the original code on non-distributed memory architectures such as the PC Beowulf cluster used for this research. Conversion routines and utilities are created to handle differences in grid formats between Corsair and the FSI module.

The resulting aeroelastic solver is tested using two simplified configurations. First, the well understood case of a flexible cylinder in cross flow is studied with the natural frequency of the cylinder set to the shedding frequency of the Von Karman streets. The cylinder is self excited and thus demonstrates the correct exchange of energy between the fluid and structural models. The second test case is based on the fourth standard configuration and demonstrates the ability of the solver to predict the dominant vibrational modes of an aeroelastic turbomachinery blade. For this case, a single blade from the fourth standard configuration is subjected to a step function from zero loading to the converged flow solution loading in order to excite the structural modes of the blade. These modes are then compared to those obtained from an in vacuo Ansys® analysis with good agreement between the two.

Committee:

Mitch Wolff, PhD (Advisor); Scott Thomas, PhD (Committee Member); Joseph Shang, PhD (Committee Member); Gary Lamont, PhD (Committee Member); David Johnston, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

FSI; Turbomachinery; CFD; Aeroelasticity

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