Doctor of Philosophy (Ph.D.), University of Dayton, 2021, Electrical and Computer Engineering

In long range imaging applications, anisoplanatic atmospheric optical turbulence imparts spatially- and temporally-varying blur and geometric distortions in acquired imagery. The ability to distinguish true scene motion from turbulence warping is important for many image processing and analysis tasks. We present two novel scene-motion detection algorithms specifically designed to operate in the presence of anisoplanatic optical turbulence. The first method is based on modeling background intensity fluctuations with a Gaussian mixture model (GMM). The GMM parameters are formed using knowledge of the theoretical turbulence tilt variance statistics derived from the Fried parameter or refractive index structure function. Thus, this new method is referred to as the Tilt Variance GMM (TV-GMM) algorithm. While most prior intensity methods use empirical temporal data to estimate a background model, this approach is based on the theoretical atmospheric tilt variance statistics. This approach effectively avoids contamination in the background statistics when true scene motion is present. The approach also considers the application of global image registration as a preprocessing step to improve performance by employing the recently developed residual tilt variance analysis that accounts for image registration as described in [1]. Rather than forming its statistical model on the (optionally registered) input imagery directly, the second method uses a turbulence simulator. Multiple realizations of atmospheric turbulence are applied to a single prototype background image to create a non-contaminated image stack of the scene background. To incorporate the spatial relationship between neighboring pixels, each pixel's intensity is treated as an independent variable of a single Gaussian distribution. Although full anisoplanatic turbulence simulators are available, alternative approaches are sufficient provided that the anisoplanatic warping is accurate. In this work, a warping (open full item for complete abstract)

Committee: Russell Hardie (Committee Chair); Vijayan Asari (Committee Member); John Loomis (Committee Member); Barry Karch (Committee Member); Thomas Wischgoll (Committee Member) Subjects: Atmospheric Sciences; Electrical Engineering

Master of Science in Electrical Engineering, University of Dayton, 2020, Electrical and Computer Engineering

We present a novel deep learning approach for restoring images degraded by atmospheric optical turbulence. We consider the case of terrestrial imaging over long ranges with a wide field of view. This produces an anisoplanatic imaging scenario where the turbulence warping and blurring varies spatially across the image. The proposed turbulence mitigation (TM) method assumes that a sequence of short exposure images are acquired. A block matching algorithm for dewarping observed frames is applied and the resulting images are averaged. A convolutional neural network (CNN) is then employed to perform spatially adaptive restoration. Training the CNN is accomplished using simulated data from a fast simulation tool that mimics turbulence effects and is capable of producing a large amount of degraded imagery from ground truth imagery rapidly. Testing is done using independent data simulated with a different well-validated and pioneering anisoplanatic turbulence simulator. The anisoplanatic simulator is known to be very accurate in modeling turbulence. However, because it is much more computationally demanding, it is used here only for producing the limited amount of testing data needed. Our proposed TM method is evaluated in a number of experiments using quantitative metrics. The quantitative analysis is made possible by virtue of having ground truth imagery that is available with simulated data. A number of restored images are also provided for subjective evaluation. We demonstrate that the new TM method outperforms all of the benchmark methods in the scenarios tested in this thesis.

Committee: Russell Hardie Ph.D. (Advisor); Eric Balster Ph.D. (Committee Member); Barry Karch Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science (M.S.), University of Dayton, 2013, Aerospace Engineering

Large Eddy Simulations (LES) are beginning to emerge as the state-of-the art for turbulence modeling in Computational Fluid Dynamics (CFD), but due to current computational constraints, the need will continue to exist for a lower fidelity, yet robust set of Reynolds-Averaged Navier- Stokes (RANS) turbulence models. Many of these turbulence models are based off of the classic Boussinesq approximation which relates the mean flow stresses to the turbulent eddy viscosity. The traditional Boussinesq approximation relies upon the instantaneous strain rate which may produce large errors in solutions for flows with significant changes in strain (such as areas of massive separation and re-attachment). The unstructured Navier-Stokes solver AVUS is modified using a new method developed by Peter E. Hamlington and Werner J. A. Dahm which replaces the classic Boussinesq approximation with a new non-equilibrium closure technique. The new non-equilibrium k omega turbulence model modification takes into account the time history of the strain rate by modifying the eddy viscosity term found in the k omega Wilcox turbulence model. Computational results from this new model are compared to experimental data from numerous test cases which include a two-dimensional flat plate, NACA 0012 airfoil, RAE 2822 transonic airfoil, and a fully three-dimensional unmanned aerial vehicle. The results of the new model are encouraging since they are more closely correlating to experimental data.

Committee: Markus Rumpfkeil (Advisor) Subjects: Aerospace Engineering

Master of Science in Mechanical Engineering (MSME), Wright State University, 2024, Mechanical Engineering

Conventional turbulence models often predict behaviors opposite as to what is observed in flows subject to rotation. In this type of flow scenario, rotation typically induces turbulence suppression. To address this limitation, a modification to the Spalart Allmaras Model with Rotation Correction (SA-R) was proposed to enhance the original Spalart Allmaras Model's sensitivity to rotation and curvature. To test the validity and accuracy of this modification, two cases were investigated. The first case involved an axisymmetric rotating pipe. A Reynolds Number of 37,000 was implemented and the initial and boundary conditions established by Zaets et. al. were utilized. Initially non-rotating, the flow transitioned to full rotation at N=0.6 at 9 m. Results demonstrated strong alignment with experimental data, showcasing improvements over the SA , SA-R, SARC, and SA-R23 models. In the second case, a vortex, surrounded by irrotational flow, was studied. This case used a Reynolds number of 10^5, and implemented the initial and boundary conditions outlined by Spalart and Garbaruk. While the modified model showed improvement over the SA model, it still displayed slight circulation overshoot, a behavior considered unphysical. However, it notably reduced the magnitude of eddy viscosity. The SARC model did produce a laminar state solution. Other vortex parameters also indicated circulation overshoot of the modified SA-R model. Overall, the modified SA-R model showed significant improvement for rotational flow scenarios and holds potential for further refinement to improve accuracy.

Committee: George Huang Ph.D., P.E. (Advisor); José Camberos Ph.D., P.E. (Committee Member); Mitch Wolff Ph.D. (Committee Member) Subjects: Fluid Dynamics

Master of Science, The Ohio State University, 2022, Mechanical Engineering

The interaction of a shock wave with a homogeneous field of acoustic waves (shock/acoustics interaction) is studied using direct numerical simulation (DNS) and linear interaction analysis (LIA). The inflow boundary condition for the DNS of shock/acoustics interaction is prescribed using the saved data of precursor DNS of boundary-layer acoustic radiation. The broadband tunnel noise radiated from the the tunnel-wall turbulent boundary layer can be well represented by an acoustic model with an ansatz of slow acoustic waves. With successful calibration of the model parameters against the precursor tunnel DNS, such an acoustic ansatz can successfully reproduce both the frequency-wavenumber spectra and the temporal evolution of the broadband tunnel noise radiated from the tunnel wall. Two canonical shock/acoustics interaction cases with a normal shock wave are conducted at Mach 2.5. The DNS results are compared with those of LIA that models linear dynamics for making distinctions between linear and nonlinear mechanisms. Good comparisons are found in the turbulent kinetic energy $\overline{u'_k u'_k}/2$, pressure fluctuation variance $\overline{p'^2}$, normal Reynolds stresses and anisotropy behind the shock between DNS and LIA. Resonably good qualitative comparisons are observed for total pressure variance $\overline{p_t'^2}$. The power spectral density (PSD) of post-shock static pressure $p'_2$ shows significant deviation from the pre-shock value at high frequencies in the near-field but it relaxes to a very similar shape to pre-shock value in the far-field. PSD of post-shock total pressure $p'_{t,2}$ seems to be similar to that of the pre-shock static pressure $p'_1$ in both near-field and far-field. Additionally, a shock/acoustic interaction case is conducted with a bow shock induced by a PCB132 Pitot probe at Mach 8. Considering the area directly in front of the sensing area where the shock is nearly stantionary and normal, the LIA results of pressure (open full item for complete abstract)

Committee: Datta Gaitonde (Committee Member); Lian Duan (Advisor) Subjects: Aerospace Engineering; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2021, Electro-Optics

Wave optics is used for modeling laser propagation through turbulence, and with laser technology maturation, the simulation space has expanded to the point that current turbulence representations via phase screens are lacking. This research eliminates such deficiencies by adopting a fractal description of turbulence in order to facilitate a noise function based phase screen. Primarily focused on aero-optical data collected using Shack-Hartmann wavefront sensors, novel analysis processes are developed that leverages off of wavelets, circular statistics, optical flow, and radial basis functions. The resulting values serve as inputs for noise function based phase screens generators supported by a dedicated physics based render engine developed from first principles. Finally, multiple wave optics simulations demonstrate the flexibility of this methodology, culminating with an airborne example that includes turret slew over the hemisphere, producing angle dependent far-field irradiance profiles distorted by localized, non-stationary turbulence.

Committee: Paul McManamon (Committee Chair); David Goorskey (Committee Member); Andrew Sarangan (Committee Member); Edward Watson (Committee Member) Subjects: Computer Science; Electromagnetics; Optics; Physics

Master of Science (M.S.), University of Dayton, 0, Electro-Optics

Optical (atmospheric) turbulence (Cn2) is a highly stochastic process that can apply many adverse effects on imaging and laser propagation systems. Modeling atmospheric turbulence conditions has been proposed by physics-based models but they are unable to capture the many cases. Recently, machine learning surrogate models have been used to learn the relationship between local environmental (weather) and turbulence conditions. These models predict a turbulence strength at time t from weather at time t. This thesis proposes a technique to forecast four hours of future turbulence conditions at 30-minute intervals from prior environmental parameters using artificial neural networks. First, local weather and turbulence measurements are formatted to pairs of input sequence and output forecast. Next, a grid search is performed to find the best combination of model architecture and training parameters. The architectures investigated are the Multilayer Perceptron (MLP) and three variants of the Recurrent Neural Network (RNN). Finally, the selected model is applied to the test dataset and analyzed. It is shown that the model has generally learned the relationship between prior environmental and future turbulence conditions.

Committee: Edward Watson (Advisor); Vijayan Asari (Committee Member); Yakov Diskin (Committee Member) Subjects: Artificial Intelligence; Physics

Doctor of Philosophy (Ph.D.), University of Dayton, 2020, Electrical and Computer Engineering

This research began as a continuation of work on the propagation of planar electromagnetic (EM) waves through a turbulent atmosphere, specifically a form of refractive index based phase turbulence modeled by the Modified von Karman Spectrum (MVKS). In the previous work within our group, EM propagation through a turbulent atmosphere under the MVKS model was investigated for essentially isoplanatic propagation, whereby the propagation from the source to the receiver progressed along a horizontal path, such that the effective structure parameter associated with the turbulence remained unchanged along the propagation. The problem was numerically set up by using the split-step propagation model, whereby the EM wave from the source (sometimes interpreted as a planar aperture) propagates alternately through non-turbulent regions (governed by standard Fresnel-Kirchhoff diffraction), and thereafter through MVKS regions where the phase turbulence occurs. A narrowly turbulent layer is described by a random 2D phase screen in the transverse plane; extended turbulence is modeled by a series of planar phase screens placed along the propagation path. In the above analyses, propagation of both uniform as well as profiled plane waves was considered. The present research commenced with investigating uniform, Gaussian and Bessel beam propagation along a turbulent path, and detailed numerical simulations were carried out relative to infinite as well as finite apertures in the source plane (including single and double slits, and single and double circular apertures), considering both non-turbulent and turbulent paths for comparison. Results were obtained in the near, far and deep far fields. The problem was further developed to include the case of anisoplanatic plane EM wave propagation over a slanted path. The turbulence structure function (Cn2) in this environment was considered to be altitude dependent, and for this purpose the Hufnagel-Valley (HV) model for the structure f (open full item for complete abstract)

Committee: Monish Chatterjee (Advisor); Partha Banerjee (Committee Member); Eric Balster (Committee Member); Maher Qumsiyeh (Committee Member) Subjects: Atmospheric Sciences; Electrical Engineering; Optics

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Electro-Optics

Synthetic aperture LADAR (SAL) has been widely investigated over the last 15 years with many studies and experiments examining its performance. Comparatively little work has been done to investigate the effect of atmospheric turbulence on SAL performance. The turbulence work that has been accomplished is in related fields or under weak turbulence assumptions. This research investigates some of the fundamental limits of turbulence on SAL performance. Seven individual impact mechanisms of atmospheric turbulence are examined including: beam wander, beam growth, beam breakup, piston, coherence diameter/length, isoplanatic angle (anisoplanatism) and coherence time. Each component is investigated separately from the others through modeling to determine their respective effect on standard SAL image metrics. Analytic solutions were investigated for the SAL metrics of interest for each atmospheric impact mechanism. The isolation of each impact mechanism allows identification of mitigation techniques targeted at specific, and most dominant, sources of degradation. Results from this work will be critical in focusing future research on those effects which prove to be the most deleterious. Previous research proposed that the resolution of a SAL system was limited by the SAL coherence diameter/length r ~_0 which was derived from the average autocorrelation of the SAL phase history data. The present research confirms this through extensive wave optics simulations. A detailed study is conducted that shows, for long synthetic apertures, measuring the peak widths of individual phase histories may not accurately represent the true resolving power of the synthetic aperture. The SAL wave structure function and degree of coherence are investigated for individual turbulence mechanisms. Phase is shown to be an order of magnitude stronger than amplitude in its impact on imaging metrics. In all the analyses, piston variation and coherence diameter make up the majority o (open full item for complete abstract)

Committee: Matthew Dierking (Committee Chair); Joseph Haus (Committee Member); Eric Magee (Committee Member); Bradley Duncan (Committee Member) Subjects: Optics; Physics

Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Master of Science (M.S.), University of Dayton, 2016, Electrical Engineering

When viewing objects over long distances, atmospheric turbulence introduces significant aberrations in imagery from optics with large apertures. We present a model for simulating turbulent effects in imagery using a technique similar to Bos and Roggemann's model [1]. This simulation will support efforts in developing innovative turbulence mitigation techniques and replacing expensive flight tests. The technique implements the commonly used split-step beam propagation method with phase screens optimally placed along the optical path. This method is used to supply a turbulence distorted point spread function (PSF) along the unique, optical path from the object to the camera aperture for each pixel of an image. The image is then distorted by scaling and summing each PSF with the appropriate surrounding area of the corresponding pixel for new pixel values. Very large phase screens have been integrated into the simulation to account for low spatial frequencies and wind speed in video. Additionally, a modified version of Schmidt's method [2] is implemented for estimating statistics for the individual phase screens in the model and for angle spectrum propagation through free space. The proposed model has the capability of simulating over horizontal or slanted paths using the Huffnagel Valley turbulence profile. For verification purposes, analysis of average simulated PSFs for short and long exposures and angle of arrival were compared to theoretical results. Further analysis of simulated error statistics were carried out against varying elevation in the atmosphere.

Committee: Russell Hardie Ph.D. (Advisor); Monish Chatterjee Ph.D. (Committee Member); Barry Karch Ph.D. (Committee Member) Subjects: Atmospheric Sciences; Computer Science; Electrical Engineering; Engineering; Optics

PhD, University of Cincinnati, 2005, Engineering : Aerospace Engineering

This work investigates the ability of algebraic Reynolds stress models to predict planar mixing layer flows, including effects caused by increasing compressibility such as the reduction in mixing layer growth rate and disproportionate reduction in individual turbulent stresses which causes an increase in turbulence anisotropy. To achieve these results a new algebraic Reynolds stress model is developed from first principles with careful consideration for incorporating additional correlation terms which arise in compressible flows. A new explicit solution procedure for the Reynolds stresses is also developed using an appropriate three-term tensor basis representation for compressible flows. This new solution procedure is moderately more complicated than existing explicit solution procedures for incompressible algebraic stress models since it requires the solution of a quartic, rather than cubic, equation for one of the tensor basis coefficients. Special consideration must also be given to the treatment of specific degenerate cases which are self-correcting in the incompressible formulation. For two-dimensional incompressible flow, the new solution procedure properly reduces to that used in existing explicit algebraic stress models. The new algebraic stress model has been calibrated against detailed experimental data for a benchmark incompressible mixing layer. To aid in this calibration an automated numerical optimization procedure was developed. This calibration yielded a new set of coefficients for the pressure-strain correlation tensor that improves the predicted incompressible mixing layer growth rate and turbulent stresses. Recent experimental data and direct numerical simulations of compressible mixing layers indicate that the observed changes in mixing layer growth rate and turbulence anisotropy are caused by reduced pressure fluctuations. This reduced communication results in changes to the turbulent length scale and pressure-strain correlation tensor. Compres (open full item for complete abstract)

Committee: Dr. Paul Orkwis (Advisor) Subjects: Engineering, Aerospace

Doctor of Philosophy in Engineering, University of Toledo, 2004, Engineering

In chemical processing industries, heating, cooling and other thermal processing of viscous fluids are an integral part of the unit operations. Consequences of improper mixing include non-reproducible processing conditions and lowered product quality. Static mixers economically promote the mixing of flowing fluid streams. One typical static mixer, the helical static mixer, consists of left- and right-twisting helical elements placed at right angles to each other. The range of Reynolds numbers of practical flows for helical static mixers in industry is usually from very small values to not very large values (e.g., Re = 5,000). This thesis describes how static mixing processes of single-phase Newtonian and also non-Newtonian liquids can be simulated numerically and provides useful information that can be extracted from the simulation results. The Turbulent flow case is solved using the most common Reynolds Averaged Navier-Stocks (RANS) models as well as Large-Eddy Simulation (LES) turbulent flow model. The numerical simulation of the mixing in the helical static mixer has been performed via a two-step procedure. In the first step, the flow velocity (and the pressure) is computed. These values are then used as input to the next step. In the second step the particle trajectory in the flow field is calculated. At the entry of the pipe inlet, a large number of marker particles are uniformly distributed over half of the flow field. This represents a simplified model for diametrical feeding of the mixer with two liquids. Using different measurement tools, such as Residence Time Distribution (RTD) and Particles Distribution Uniformity (PDU), the performance of a six-element helical static mixer is studied. It is shown that the Reynolds number has a major impact on the performance of a static mixer. It is also shown that the performance of a helical static mixer is different for Newtonian and non-Newtonian fluids in non-creeping flows. Finally, heat transfer within a helical (open full item for complete abstract)

Committee: Theo Keith (Advisor) Subjects: Engineering, Mechanical

Master of Science (M.S.), University of Dayton, 2011, Electro-Optics

Atmospheric turbulence affects optical systems that operate in various atmospheric conditions. The characteristics of the optical wave transmitted through atmospheric turbulence can undergo dramatic changes resulting in potential system performance degradation. Knowledge of atmospheric turbulence effects would aid in the development of a wide class of atmospheric-optics systems including laser communication, directed energy, lidar, remote sensing, and active and passive imaging systems. In the classical atmospheric turbulence theory, the refractive index structure parameter is the key parameter known to describe the strength of the atmospheric turbulence and accurate measurement of this parameter represents an important task. The refractive index structure parameter can be difficult to measure, as it is influenced by many factors including path length, time of day, season, and microclimate conditions which cannot be applied universally and may change in a matter of minutes. To further complicate atmospheric turbulence characterization, the key assumptions of classical (Kolmogorov) turbulence theory, such as statistical homogeneity and isotropy of the refractive index random field, are not always satisfied. From this viewpoint, experimental analyses to determine the applicability of the Kolmogorov turbulence theory in different optical wave propagation conditions represent important tasks and can assist in the adequate evaluation of atmospheric turbulence effects on optical system performance and design. In this thesis, the applicability of the classical turbulence theory was verified through simultaneous intensity measurements (pupil- and focal-plane intensity distributions) from multi-wavelength laser beacons over a near-ground, near-horizontal, and seven-kilometer-long propagation path. These measurements allowed independent evaluation of the refractive index structure parameter for two different wavelengths (λ1 = 532 nm, λ2 = 1064 nm), and these results were comp (open full item for complete abstract)

Committee: Mikhail A. Vorontsov PhD (Committee Chair); Joseph W. Haus PhD (Committee Member); Edward A. Watson PhD (Committee Member) Subjects: Engineering; Optics; Physics

Doctor of Philosophy, University of Akron, 2007, Mechanical Engineering

The relationship between the onset of Taylor instability and appearance of what is commonly known as “turbulence” in narrow gaps between two cylinders is investigated. A question open to debate is whether the flow formations observed during Taylor instability regimes are, or are related to the actual “turbulence” as it is presently modeled in micro-scale clearance flows. This question is approached by considering the viscous fluid flow in narrow gaps between two cylinders with various eccentricity ratios. The computational engine is provided by CFD-ACE+, a commercial multi-physics software. The flow patterns, velocity profiles and torques on the outer cylinder are determined when the speed of the inner cylinder, clearance and eccentricity ratio are changed on a parametric basis. Calculations show that during the Taylor and wavy vortex regime velocity profiles in the radial direction are sinusoidal with pressure variations in the axial direction even for the case of the “long journal bearing” (L/D>2). Based on these findings, a new model for predicting the flow behavior in long and short journal bearing films in the transition regime is proposed. Unlike the modified turbulent viscosity of the most accepted models (Constantinescu, Ng-Pan, Hirs and Gross et al.), the viscosity used in the new model is kept at its laminar value. Experimental torque measurements and flow visualization are performed for three kinds of oils with different viscosities. It is shown that in general there is a good agreement between the numerical and experimental torques except those in turbulent regime. Comparison between numerical and experimental flow patterns is also made and it shows that they match well in the Couette, Taylor and Wavy regimes. In general there is a good agreement between the numerical and experimental results including torque measurements and flow patterns. The new model for predicting the flow behavior in journal bearing films in the transition regime is justified.

Committee: Minel Braun (Advisor) Subjects: Engineering, Mechanical

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1965, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1962, Graduate School

Committee: Not Provided (Other) Subjects:

PHD, Kent State University, 2024, College of Communication and Information

Personalization for users can be a desired outcome of their interactions with social media algorithms (e.g., liking certain content to suggest they want more of it). This level of interaction can depend on users' awareness and affective evaluations of the algorithm. However, considering these two contextual influences, how do users perceive and subsequently act in response to social media algorithms predicting private information about the user that they do not wish the algorithm to know or understand? Over the course of two online survey studies, this dissertation integrates the Communication Privacy Management (CPM) theoretical framework (Petronio, 2002; 2013) into the human-machine communication (HMC) context. Users' experiences of privacy breakdowns and recalibration strategies with social media algorithms collected in the first study were used to develop and test two preliminary measures: the algorithmic privacy breakdown measure and the algorithmic privacy repair measure. We argued that, in addition to the preliminary measure, users' awareness of and attitudes towards social media algorithms, both positive and negative, play a crucial role in predicting their interaction behavior, regulating their desired co-ownership (i.e., granting the algorithm access to private information), and determining how the degree of co-ownership influences their breakdown experiences and the strategies they employ to rectify these breakdowns. Results suggest that greater positive attitudes predict greater co-ownership of private information with the algorithm. However, greater awareness and negative attitudes predict the inverse. Those with more awareness and negative attitudes are less likely to allow private information to be known by social media algorithms. Breakdown experiences involving targeted ads related to intimate personal information led to greater use of recalibration practices that adjust their platform settings, resemble human-algorithm interplay, and severe pulling (open full item for complete abstract)

Committee: Michael Beam (Committee Chair); Jeffrey Child (Advisor); Mina Choi (Committee Member); Judith Gere (Committee Member) Subjects: Communication; Computer Science; Information Science; Quantitative Psychology; Social Psychology

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Aerospace Engineering

Understanding and characterization of turbulence over the flight deck of large marine vehicle is important to assess its influence on the helicopter pilot workload while performing launch and recovery maneuvers. This research is regarding understanding the turbulent flow field over the flight deck of simplified frigate model (SFS2) using an Embedded Large Eddy Simulation turbulence model. The characterization of integral time and length scales of turbulent vortical structures in the superstructure air wake is carried out using correlation analysis. Focus of this research work is to understand the underlying reasoning of the generation of bistable airwake of the superstructure, asymmetry in the mean airwake structure and to ascertain the influence of its upstream flow field on the nature and characteristics of airwake. The asymmetry in the mean airwake behind superstructure was attributed to “locking” and/or differential momentum flux on sides of superstructure in literature, however no concrete evidence of causation was reported. In this research, the in-depth analysis of turbulent boundary layer buildup, vorticity distribution, relative size and orientation of vortices on and along the starboard and port sides of superstructure provides clear understanding and evidence of the influence of bow region flow field on airwake. The dynamics of bow flow field and vortical structures like leading edge vortices and horseshoe base vortex, generated upstream of superstructure forward facing step (bow-superstructure junction), and their possible interaction is investigated to ascertain their contribution towards the generation of asymmetrical mean airwake of superstructure. The time averaged flow field analysis revealed that bow flow field and the nature of the interaction between its leading edge vortices on the port and starboard sides respectively, with the base vortex highly influence the turbulence generation on the sides of the superstructure and ultimately influence the (open full item for complete abstract)

Committee: Peter Disimile Ph.D. (Committee Chair); Prashant Khare Ph.D. (Committee Member); Shaaban Abdallah Ph.D. (Committee Member) Subjects: Aerospace Materials