Mechanical Engineering Commons^™

The Influence Of Non-Equilibrium Pressure On Rotating Flows, Irfan Rashid Zardadkhan

Mechanical & Aerospace Engineering Theses & Dissertations

This study was undertaken to investigate the influence of pressure relaxation on steady, incompressible flows with strong streamline curvature. In the early part of this dissertation research, the significance of non-equilibrium pressure forces in controlling the structure of a steady, two dimensional axial vortex was demonstrated. In order to extend the study of pressure relaxation influences on more complex rotating flows, this dissertation has examined other rotating flow features that can be associated with hurricanes, tornadoes and dust devils. To model these flows, modified boundary layer equations were developed for a fluid column rotating near a solid plane including the …

Modeling, Identification, Validation And Control Of A Hybrid Maglev Ball System, Ahmed Elhussein E. Mekky

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, the electrodynamics of a single axis hybrid electromagnetic suspension Maglev system was modeled and validated by applying it to a single axis hybrid maglev ball experiment. By exploring its linearized model, it was shown that the single axis hybrid Maglev ball has inherently unstable dynamics. Three control scenarios were explored based on the linearized model; (1) Proportional, Deferential (PD) control, (2) Proportional, Deferential, Integral (PID) and (3) PID controller with pre-filtering. This thesis has shown that a PID controller with a pre-filtering technique can stabilize such a system and provide a well-controlled response.

A parametric system identification …

Numerical Study Of The Performance Of A Model Scramjet Engine, Ayad Alhumadi

Mechanical & Aerospace Engineering Theses & Dissertations

A computational parametric investigation was conducted to study the effect of variations to several geometric parameters on the performance of a two-dimensional model scramjet engine (square cross section area for 3-D model). Geometric parameters included backstep location, height, and angle and fuel injector angle, diameter, and location. Two- and three-dimensional geometries have been studied, using a finite-volume computational fluid dynamics (CFD) code (FLUENT) with structured grids with sizes between 50,000 and 90,000 cells for the two-dimensional geometry and with structured hexahedral grid sizes between 650,000 and 949,725 cells for the three-dimensional geometry. Otherwise, identical values of program inputs were utilized …

Molecular Dynamics Studies On Nanoscale Gas Transport, Murat Barisik

Mechanical & Aerospace Engineering Theses & Dissertations

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress …

Dynamics And Control Of Satellite Relative Motion In Proximity Operations, Mohamed Elsayed Aly Abd Elaziz Okasha

Mechanical & Aerospace Engineering Theses & Dissertations

In this dissertation, the development of relative navigation, guidance, and control algorithms of an autonomous space rendezvous and docking system are presented. These algorithms are based on innovative formulations of the relative motion equations that are completely explicit in time. The navigation system uses an extended Kalman filter based on these formulations to estimate the relative position and velocity of the chaser vehicle with respect to the target vehicle and the chaser attitude and gyro biases. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system, along with the star …

Large-Eddy Simulation Of Axially-Rotating, Turbulent Pipe And Particle-Laden Swirling Jet Flows, Nicolas D. Castro

Mechanical & Aerospace Engineering Theses & Dissertations

The flows of fully-developed turbulent rotating pipe and particle-laden swirling jet emitted from the pipe into open quiescent atmosphere are investigated numerically using Large-Eddy Simulation (LES). Simulations are performed at various rotation rates and Reynolds numbers, based on bulk velocity and pipe diameter, of 5.3x103, 12x103, and 24x103, respectively. Time-averaged LES results are compared with experimental and simulation data from previous studies. Pipe flow results confirm observations in previous studies, such as the deformation of the turbulent mean axial velocity profile towards the laminar Poiseuille-profile, with increased rotation. The Reynolds stress anisotropy tensor shows a redistribution due to pipe rotation. …