Search Results (1 - 3 of 3 Results)

Sort By  
Sort Dir
 
Results per page  

Rinehart, Aidan WalkerA Characterization of Seal Whisker Morphology and the Effects of Angle of Incidence on Wake Structure
Master of Science in Mechanical Engineering, Cleveland State University, 2016, Washkewicz College of Engineering
Seal whiskers have been found to produce unique wake flow structures that minimize self-induced vibration and reduce drag. The cause of these wake features are due to the peculiar three-dimensional morphology of the whisker surface. The whisker morphology can be described as an elliptical cross section with variation of diameter in the major and minor axis along the length and, angle of incidence, rotation of the elliptical plane with respect to the whisker axis, α at the peak and β at the trough. This research provided a more complete morphology characterization accomplished through CT scanning and analysis of 27 harbor and elephant seal whisker samples. The results of this study confirmed previously reported values and added a characterization of the angle of incidence finding that the majority of angles observed fall within ±5° and exhibit a random variation in magnitude and direction along the whisker length. While the wake effects of several parameters of the whisker morphology have been studied, the effect of the angle of incidence has not been well understood. This research examined the influence of the angle of incidence on the wake flow structure through series of water channel studies. Four models of whisker-like geometries based on the morphology study were tested which isolate the angle of incidence as the only variation between models. The model variations in angle of incidence selected provided a baseline case (α = β = 0°), captured the range of angles observed in nature (α = β = -5°, and α = β = -15°), and investigated the influence of direction of angle of incidence (α = -5°, β = -5°). The wake structure for each seal whisker model was measured through particle image velocimetry (PIV). Angle of incidence was found to influence the wake structure through reorganization of velocity field patterns, reduction of recovery length and modification of magnitude of Tu. The results of this research helped provide a more complete understanding of the seal whisker morphology relationship to wake structure and can provide insight into design practices for application of whisker-like geometry to various engineering problems.

Committee:

Wei Zhang, PhD (Advisor); Ibrahim Mounir, PhD (Committee Member); Shyam Vikram, PhD (Committee Member)

Subjects:

Aerospace Engineering; Aquatic Sciences; Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

seal; whisker; PIV; biomimicry; fluid dynamics; particle image velocimetry; bio-engineering; engineering; mechanical engineering; aerospace engineering; experimental fluid dynamics;

Buettner, Robert W.Dynamic Modeling and Simulation of a Variable Cycle Turbofan Engine with Controls
Master of Science in Mechanical Engineering (MSME), Wright State University, 2017, Mechanical Engineering
Next generation aircraft (especially combat aircraft) will include more technology and capability than ever before. This increase in technology comes at the price of higher electrical power requirements and increased waste heat that must be removed from components to avoid overheating induced shutdowns. To help combat the resulting power and thermal management problem, a vehicle level power and thermal management design and optimization toolset was developed in MATLAB®/Simulink®. A dynamic model of a three-stream variable cycle engine was desired to add to the capabilities of the power and thermal management toolset. As an intermediate step to this goal, the dynamic mixed-flow turbofan engine model previously developed for the toolset was modified with an afterburner, a variable geometry nozzle, and a new controller to automatically control the new components. The new afterburning turbofan engine model was tested for a notional mission profile both with and without power take-off. This testing showed that the afterburning turbofan engine model and controller were successful enough to justify moving on to the development of the three-stream variable cycle engine model. The variable cycle engine model was developed using the components of the afterburning turbofan model. The compressor and turbine components were modified to use maps that incorporate the effects of variable inlet guide vane angles. The new engine model and components were sized by attempting to match data from a Numerical Propulsion System Simulation model with similar architecture. A previously developed heat exchanger model was added to the third stream duct of the new engine model. Finally, a new simplified controller was developed for the variable cycle engine model based on the controller developed for the afterburning turbofan model. The new variable cycle engine model was tested for a notional mission profile for five cases. The first case operated the engine model without power take-off and with the third stream heat exchanger removed. The second case added shaft power take-off. The third and fourth cases did away with the power take-off and added the heat exchanger to the engine model with two different hot-side mass flow rate conditions. The fifth case tested the engine with both power take-off and the third stream heat exchanger. The results were promising, showing that the variable cycle engine model had variable cycle tendencies even with a minimum of controlled variable geometry features. The controller was found to be effective, though in need of upgrades to take advantage of the benefits offered by a variable cycle engine. Additionally, it was found that both power take-off and heat rejection to the third stream impact the entire engine cycle.

Committee:

Rory Roberts, Ph.D. (Advisor); Mitch Wolff, Ph.D. (Committee Member); Rolf Sondergaard, Ph.D. (Committee Member); Robert Fyffe, Ph.D. (Other)

Subjects:

Aerospace Engineering; Mechanical Engineering

Keywords:

mechanical engineering; aerospace engineering

Raja, Muneeb MasoodExtended Kalman Filter and LQR controller design for quadrotor UAVs
Master of Science in Electrical Engineering (MSEE), Wright State University, 2017, Electrical Engineering
A quadrotor is a unique class of UAVs with vertical take off and landing (VTOL) capability and has attracted significant attention due to its importance in various applications. This thesis presents the design and experimental implementation of Extended Kalman Filters (EKFs) to estimate the states of a quadrotor and a Linear Quadratic Regulator (LQR) controller with integral action to meet the desired control objectives. In case of the Extended Kalman Filters, two different situations are considered: (1) all the states including the Inertial Measurement Unit (IMU) biases are estimated; (2) only the attitude, altitude, and vertical velocity are estimated. The second case is added as a safety feature to provide enough feedback signals to stabilize and land the quadrotor in the event of a position measurement loss, e.g. from a GPS due to jamming. A double loop control structure is implemented using an LQR controller with integral action, the inner loop contains the attitude and the altitude control, and the outer loop consists of x and y translational positions control. Finally, some preliminary results on the integration of C codes with Simulink using C MEX S-functions is described. A C library of a laser rangefinder sensor is transferred to a C MEX S-function to generate a 2D map of the environment using the laser sensor distance measurements to identify obstacles present within the range of the sensor. The concept of multi-threading and the integration of pthread library with Simulink using C MEX S-function are also described.

Committee:

Xiaodong Zhang, Ph.D. (Advisor); Kuldip Rattan, Ph.D. (Committee Member); Jonathan Muse, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering

Keywords:

electrical engineering; aerospace engineering