Engineering Commons^™

Channel Flow Behaviour During Mixed Convection At Low Reynolds Numbers, Ahmed Elatar

Electronic Thesis and Dissertation Repository

The effect of mixed convection on low Reynolds numbers flow inside a horizontal square channel heated from below have been investigated experimentally. The channel flow rate ranged from 0.0210 kg/s to 0.0525 kg/s which correspond to Reynolds numbers between 300 and 750 in the absence of heating. The channel bottom surface temperature was controlled and varied from 30 ºC to 55 ºC (Grashof number ranged between 6.37×10⁶ and 3.86×10⁷). Planer Particle Image Velocimetry (PIV) technique was used to measure two-dimensional velocity fields in the channel mid-vertical plane and two horizontal planes close to the bottom heated wall. …

Microphone-Based Pressure Diagnostics For Boundary Layer Transition, Spencer Everett Lillywhite

Master's Theses

An experimental investigation of the use low-cost microphones for unsteady total pressure measurement to detect transition from laminar to turbulent boundary layer flow has been conducted. Two small electret condenser microphones, the Knowles FG-23629 and the FG-23742, were used to measure the pressure fluctuations and considered for possible integration with an autonomous boundary layer measurement system. Procedures to determine the microphones’ maximum sound pressure levels and frequency response using an acoustic source provided by a speaker and a reference microphone. These studies showed that both microphones possess a very flat frequency response and that the max SPL of the FG-23629 …

Verification And Validation Of The Spalart-Allmaras Turbulence Model For Strand Grids, Oisin Tong

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The strand-Cartesian grid approach is a unique method of generating and computing fluid dynamic simulations. The strand-Cartesian approach provides highly desirable qualities of fully-automatic grid generation and high-order accuracy. This thesis focuses on the implementation of the Spalart-Allmaras turbulence model to the strand-Cartesian grid framework. Verification and validation is required to ensure correct implementation of the turbulence model.

Mathematical code verification is used to ensure correct implementation of new algorithms within the code framework. The Spalart-Allmaras model is verified with the Method of Manufactured Solutions (MMS). MMS shows second-order convergence, which implies that the new algorithms are correctly implemented.

Validation …

The Determination Of Drag And Lift Forces Of A Rigid Beam Located Within A Turbulent Boindary Layer By Means Of Large Eddy Simulation Modeling, Santiago Helman

Dissertations and Theses

"Recent studies such as those conducted by Akaydin, Elvin and Andreopoulos in [1] have described and quantified the electrical power that can be extracted from a moving flow by the implementation of energy harvesters. In such study, a flexible cantilevered beam was fitted with a cylindrical prism at the free end and placed within a uniform flow field. Due to the vortex shedding generated by the prism (e.g. Von Karman vortices) the beam was found to oscillate about the undisturbed position. The beam in question was then outfitted with a piezoelectric material in order to translate the transient strain energy …

Experimental Characterization Of Roughness And Flow Injection Effects In A High Reynolds Number Turbulent Channel, Mark A. Miller

Theses and Dissertations--Mechanical Engineering

A turbulent channel flow was used to study the scaling of the combined effects of roughness and flow injection on the mean flow and turbulence statistics of turbulent plane Poiseuille flow. It was found that the additional momentum injected through the rough surface acted primarily to enhance the roughness effects and, with respect to the mean flow, blowing produced similar mean flow effects as increasing the roughness height. This was not found to hold for the turbulence statistics, as a departure from Townsend’s hypothesis was seen. Instead, the resulting outer-scaled streamwise Reynolds stress for cases with roughness and blowing deviated …

Electrokinetic Mixing And Separation In Microfluidic Systems, Fang Yang

Theses and Dissertations

Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics …

Large Eddy Simulation And Analysis Of Shear Flows In Complex Geometries, Prasad Mohanrao Kalghatgi

LSU Doctoral Dissertations

In the present work, large eddy simulation is used to numerically investigate two types of shear flows in complex geometries, (i) a novel momentum driven countercurrent shear flow in dump geometry and (ii) a film cooling flow (inclined jet in crossflow). Verification of subgrid scale model is done through comparisons with measurements for a turbulent flow over back step, present cases of counter current shear and film cooling flow. In the first part, a three dimensional stability analysis is conducted for countercurrent shear flow using Dynamic mode decomposition and spectral analysis. Kelvin-Helmholtz is identified as primary instability mechanism and observed …