Engineering Commons^™

Methods For Identifying Acoustic Emissions From The Front Face Of A Small Piezoelectric Blower, Brad K. Solomon

Theses and Dissertations

This thesis focuses on identifying acoustic noise generating components in piezoelectric blowers through transverse velocity measurements and the development of a numerical fluid model. Piezoelectric ceramics have proven useful for many industries and areas of research involving: high precision actuators, noise control, ultrasonic devices, and many other areas. As of late, a unique adaptation of piezoelectric ceramics is surfacing in the area of pumping and cooling. Air pumps that use these ceramics replace the traditional electric motor, resulting in lower power consumption, less moving parts, constant pressure gradients, lower overall weight, and a low profile. The current drawback of this …

A Study On Small Scale Intermittency Using Direct Numerical Simulation Of Turbulence, Saba Almalkie

Open Access Dissertations

Theory of turbulence at small scales plays a fundamental role in modeling turbulence and in retrieving information from physical measurements of turbulent flows. A systematic methodology based on direct numerical simulations of turbulent flows is developed to investigate universality of small scale turbulence. Understanding characteristics of the small scale intermittency in turbulent flows and the accuracy of the models, measurements, and theories in predicting it are the main objectives. The research is designed to address two central questions; 1) possible effects of large scale anisotropies on the small scale turbulence and 2) potential biases in characterizing small scale turbulence due …

The Oriented-Eddy Collision Model, Michael Bernard Martell Jr.

Open Access Dissertations

The physical and mathematical foundations of the Oriented-Eddy Collision turbulence model are provided through a discussion of the Reynolds averaged Navier-Stokes (RANS) equations, probability density functions (PDF), PDF collision models, Reynolds stress transport models (RSTM), and two-point correlations. Behavior of the Oriented-Eddy Collision turbulence model near solid boundaries is examined in depth. The Oriented-Eddy Collision turbulence model treats turbulence in a novel way: the average behavior of a turbulent flow can be modeled as a collection of interacting fluid particles, or eddies, which have inherent orientation. The model is cast in the form of a collection of Reynolds stress transport …

Evaluation Of Turbulence Variable Distributions For Incompressible Fully Rough Pipe Flows, Emilie B. Fowler

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The specific turbulent kinetic energy, root-mean-square fluctuating vorticity, and mean-vortexwavelength distributions are presented for fully rough pipe flow. The distributions of these turbulence variables are obtained from a proposed turbulence model. Many of the turbulence models commonly used for computational fluid dynamics are based on an analogy between molecular and turbulent transport. However, traditional k-ε and k-ω models fail to exhibit proper dependence on the molecular viscosity. Based on a rigorous application of the Boussinesq’s hypothesis, Phillips proposed a vorticity-based transport equation for the turbulent kinetic energy. The foundation for this vorticity-based transport equation is presented. In future development of …

Numerical Simulation Of Buoyancy-Driven Turbulent Ventilation In Attic Space Under Winter Conditions, Shimin Wang, Zhigang Shen, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Attic design and construction have significant impacts on residential buildings’ energy performance. In order to understand how passive ventilation rates affect ridge-vent attic’s performance, a two-dimensional steady-state finite volume model is employed to simulate the buoyancy-driven turbulent ventilation and heat transfer in a triangular attic space of a gable-roof residential building under winter conditions. The modeled attic has a pitch of 5/12 and a passive ventilation system, consisting of continuous ridge and soffit vents. The v2f model is used to analyze the turbulent air flow and natural convection heat transfer inside the attic. The effects of ambient air temperature, vent …

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. …

Experimental Characterization Of Baffle Plate Influence On Turbulent And Cavitation Induced Vibrations In Pipe Flow, Gavin J. Holt

Theses and Dissertations

Turbulent and cavitation induced pipe vibration is a large problem in industry often resulting in pipe failures. This thesis provides an experimental investigation on turbulent flow and cavitation induced pipe vibration caused by sharp edged baffle plates. Due to large pressure losses across a baffle plate, cavitation can result. Cavitation can be destructive to pipe flow in the form of induced pipe wall vibration and cavitation inception. Incipient and critical cavitation numbers are design points that are often used in designing baffle plate type geometries. This investigation presents how these design limits vary with the influencing parameters by exploring a …

Turbulence Modeling Of Strongly Heated Internal Pipe Flow Using Large Eddy Simulation, Michal Hradisky

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The main objective of this study was to evaluate the performance of three Large Eddy Simulation (LES) subgrid scale (SGS) models on a strongly heated, low Mach number upward gas flow in a vertical pipe with forced convection. The models chosen for this study were the Smagorinsky-Lilly Dynamic model (SLD), the Kinetic Energy Transport model (KET), and the Wall-Adaptive Local-Eddy viscosity model (WALE). The used heating rate was sufficiently large to cause properties to vary significantly in both the radial and streamwise directions. All simulations were carried out using the commercial software FLUENT.

The effect of inlet turbulence generation techniques …

Multidimensional Modeling Of Condensing Two-Phase Ejector Flow, Michael F. Colarossi

Masters Theses 1911 - February 2014

Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated.

The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The transport equations for mass and momentum treat the two phases as a continuous mixture. The fluid is treated as …

Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich

Electronic Theses and Dissertations

Recent work has shown that spatial correlation of surface pressure fluctuations in a fully turbulent atmospheric boundary layer (ABL) can give information about the velocity field and turbulence. This is of particular importance to the future of wind energy to predict the incoming velocity flow field of wind turbines so as to actively control them for peak operating efficiency and damage reduction. All of the environmental effects on the surface pressure fluctuations need to be fully understood before a suitable flow prediction algorithm can be constructed. One such environmental effect which has not been previously studied is the effect of …

Design, Fabrication And Characterization Of A New Wind Tunnel Facility – Linear Cascade With A Wake Simulator, Jean-Philippe Junca-Laplace

LSU Master's Theses

A new wind tunnel has been designed and constructed at the LSU Mechanical Engineering Laboratories. The objective was to design a versatile test facility, suitable for a wide range of experimental measurements on turbine blades. The future study will investigate the impact of unsteady inflow conditions on film cooling performance. More specifically, it will study how the unsteady flow due to the upstream passing wakes coming from the front row vane affects the film cooling performances on the turbine blades. The test section consists of a four passage linear cascade composed of three full blades and two shaped wall blades. …

A Study Of The Statistics Of The Air/Water Interfacial Temperature Field During Mixed Convection Heat Transfer, Jie Kou

All Dissertations

Heat transfer across an air/water interface is of particular importance to limnology, oceanography and some industrial applications. The relationship between the statistics of the air/water interfacial temperature field and the interfacial heat flux is poorly understood, particularly for the mixed convection condition, which is a common heat transfer mechanism for small inland lakes. The few studies that have been conducted under mixed convection conditions have been limited to an uncontrolled surfactant condition (tap water). Therefore, in this dissertation research two sets of experiments for wind speeds from 0 to 4 m/s were conducted: controlled surfactant contaminated conditions (with oleyl alcohol) …

Toward The Validation Of Depth-Averaged, Steady-State Simulations Of Fluvial Flows Using Three-Dimensional, Steady-State, Rans Turbulence Models, Pedro Abdiel Mateo Villanueva

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Calculations of fluvial flows are strongly influenced by geometry complexity and large overall uncertainty on every single measurable property, such as velocity and shear. Moreover, a considerable portion of the data obtained from computational simulations arose from two-dimensional, steady-state models. The present work states a different approach to perform computer-based simulations and analyze fluvial flows. For the first part, the suitability of OpenFOAM to be used as the main CFD solver to analyze fluvial flows is studied. Initially, two well documented channel configurations are computationally studied using OpenFOAM. Finally, these results are compared to the output obtained from one of …

Macroinstability And Perturbation In Turbulent Stirred Tank Flows, Somnath Roy

LSU Doctoral Dissertations

Impeller stirred tank reactors (STRs) are commonly used in the chemical processing industries for a variety of mixing and blending technologies. In this research, a numerical study of flow and mixing inside turbulently agitated STRs are carried out. An immersed boundary method (IBM) is utilized to represent moving impeller geometries in the background of multi-block structured curvilinear fluid. The IBM This curvilinear-IBM methodology is further combined with the large eddy simulation (LES) technique to address the issue of modeling unsteady turbulent flows in the STR. Verification of the combined IBM-LES implementation strategy in curvilinear coordinates is done through comparisons with …

Experimental Characterization Of Flow Induced Vibration In Turbulent Pipe Flow, Andrew S. Thompson

Theses and Dissertations

This thesis presents results of an experimental investigation that characterizes the wall vibration of a pipe with turbulent flow passing through it. Specifically, experiments were conducted using a water flow loop to address three general phenomena. The topics of investigation were: 1) How does the pipe wall vibration depend on the average flow speed, pipe diameter, and pipe thickness for an unsupported pipe? 2) How does the behavior change if the pipe is clamp supported at various clamping lengths? 3) What influence does turbulence generation caused by holed baffle plates exert on the pipe response? A single pipe material (PVC) …

Analysis Of Induced Vibrations In Fully-Developed Turbulent Pipe Flow Using A Coupled Les And Fea Approach, Thomas P. Shurtz

Theses and Dissertations

Turbulent flow induced pipe vibration is a phenomenon that has been observed but not fully characterized. This thesis presents research involving numerical simulations that have been used to characterize pipe vibration resulting from fully developed turbulent flow. The vibration levels as indicated by: pipe surface displacement, velocity, and acceleration are characterized in terms of the parameters that exert influence. The influences of geometric and material properties of the pipe are investigated for pipe thickness in the range 1 to 8 mm at a diameter of 0.1015 m. The effects of pipe elastic modulus are explored from 3 to 200 GPa. …

Drag Reduction In Turbulent Flows Over Micropatterned Superhydrophobic Surfaces, Robert J. Daniello

Masters Theses 1911 - February 2014

Periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide drag reduction in the laminar flow regime, have been demonstrated capable of reducing drag in the turbulent flow regime as well. Superhydrophobic surfaces contain micro or nanoscale hydrophobic features which can support a shear-free air-water interface between peaks in the surface topology. Particle image velocimetry and pressure drop measurements were used to observe significant slip velocities, shear stress, and pressure drop reductions corresponding to skin friction drag reductions approaching 50%. At a given Reynolds number, drag reduction was found to increase with increasing feature size and spacing, as in …

Effect Of Rib Turbulators On Heat Transfer Performance In Stationary Ribbed Channels, Aravind Rohan Sampath

ETD Archive

The thermal performance was examined computationally for the stationary channels with rib turbulators oriented at 90 degrees. Ribs were placed on opposite walls and the heat transfer coefficients and frictional loss were calculated. Three stationary channels with aspect ratios (W/H) 1, 2 and 4 were considered for the analysis. The thermal performance was measured by calculating the Nusselt number and frictional losses. Square ribs (w/e = 1) were considered as the baseline configuration. The rib width and rib spacing varies while the rib height is maintained constant. Rib spacing (P/e) of 10 and 20 and rib width to rib height …

Computational And Experimental Investigation Of The Flow Structure And Vortex Dynamics In The Wake Of A Formula 1 Tire, John Axerio, Gianluca Iaccarino, Emin Issakhanian, Chris Elkins, John Eaton

Mechanical Engineering Faculty Works

The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel was examined experimentally in order to assess the accuracy of different turbulence modeling techniques. The results of steady RANS and Large Eddy Simulation (LES) were compared with PIV data, which was obtained within the same project. The far wake structure behind the wheel was dominated by two strong counter-rotating vortices. The locations of the vortex cores, extracted from the LES and PIV data as well as computed using different RANS models, showed that the LES predictions are closest to the …

Introductory Lectures On Turbulence: Physics, Mathematics And Modeling, James M. Mcdonough

Mechanical Engineering Textbook Gallery

From Chapter 1:

The understanding of turbulent behavior in flowing fluids is one of the most intriguing, frustrating— and important—problems in all of classical physics.

The problem of turbulence has been studied by many of the greatest physicists and engineers of the 19th and 20th Centuries, and yet we do not understand in complete detail how or why turbulence occurs, nor can we predict turbulent behavior with any degree of reliability, even in very simple (from an engineering perspective) flow situations. Thus, study of turbulence is motivated both by its inherent intellectual challenge and by the practical utility of a …

Turbulence Modeling For Film Cooling Flows, Asif Hoda

LSU Doctoral Dissertations

An improved two equation turbulence model has been developed in this dissertation to better predict the complex film cooling flow field that is formed from the interaction of a coolant jet and a crossflow over a modeled turbine blade surface. Film cooling of turbine blades is commonly employed to effectively protect turbine blades from thermal failure and thereby to allow higher inlet temperatures in order to increase the efficiency of gas turbine engines. Film cooling involves the injection of rows of coolant jets from slots on the surface of a turbine blade which is then bent over by the crossflow …

Developing Dns Tools To Study Channel Flow Over Realistic Plaque Morphology, Ryan M. Beaumont

Electronic Theses and Dissertations

In a normal coronary artery, the flow is laminar and the velocity is parabolic in nature. Over time, plaques deposit along the artery wall, narrowing the artery and creating an obstruction, a stenosis. As the stenosis grows, the characteristics of the flow change and transition occurs, resulting in turbulent flow distal to the stenosis. To date, direct numerical simulation (DNS) of turbulent flow has been performed in a number of studies to understand how stenosis modifies flow dynamics. However, the effect of the actual shape and size of the obstruction has been disregarded in these DNS studies. An ideal approach …

Numerical Simulation Of Plasma-Based Actuator Vortex Control Of A Turbulent Cylinder Wake, Nathan Keith Mcmullin

Theses and Dissertations

A numerical study has been performed to investigate the mechanics of the turbulent wake of a circular cylinder that is controlled by a plasma actuator. The numerical investigation implements a straightforward moving wall boundary condition to model the actuator's effects on the flow. Validations of the moving wall for this simulation are set forth with the understanding that the moving wall can model the plasma actuator bulk flow effects at a distance downstream and not in a region near or on the plasma actuator. The moving wall boundary condition is then applied to a circular cylinder at a Reynolds number …

A Lagrangian Stochastic Model For Dispersion In Stratified Turbulence, S. K. Das, Paul A. Durbin

Paul A. Durbin

In this paper we discuss the development of a Lagrangian stochastic model (LSM) for turbulent dispersion of a scalar (species). Given any tensorally linear second-moment closure (SMC) turbulence model we show how to derive a mathematically equivalent set of stochastic differential equations (SDEs), i.e., the second-moment equations constructed from these SDEs are exactly the same (within a realizability constraint) as the given SMC. This set of equations forms the LSM. Both turbulence anisotropy and buoyancy effects are incorporated by this method. In order to achieve the correct critical Richardson number and to obtain the simplest Lagrangian formulation, a revised set …

Large Eddy Simulation Based Turbulent Flow-Induced Vibration Of Fully Developed Pipe Flow, Matthew Thurlow Pittard

Theses and Dissertations

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES …

Effect Of Unsteady Wake, Free Stream Turbulence, Tip Geometry On Blade Tip Flow And Heat Transfer, Vikrant Saxena

LSU Master's Theses

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer. The linear cascade is made of four blades scaled up HPT turbine in a low speed wind tunnel facility with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116 degree turn in the flow through the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83e5. The center blade …

Numerical Investigation Of Flow Through Wide Angle Diffusers, Moududur Rahman

Dissertations

This study is aimed at the development of a computational technique for the prediction of the flow field in wide angle diffusers. The finite element technique is used for the solution of the governing equations. A commercial software package, NISA/3DFlUID, modified for this specific application was used. The parameters affecting the flow field have been identified. For a wide range of variation of these parameters, the effects on the flow field have been examined. This investigation is an exhaustive and comprehensive numerical study of diffuser flows. Such a study will result in substantial improvement in the understanding of the anatomy …

An Investigation Of The Formation Of Turbulent Water And Abrasive Water Jets, Md. Ekramul Hasan Khan

Dissertations

This study is concerned with the development of a knowledge base for the selection of nozzle geometry by investigating the mechanism of formation and behaviors of water and abrasive water jets. A numerical prediction of turbulent water flow inside various nozzles is developed. The analysis is based on the numerical solution of conservation equations of continuity and momentum as well as equations of turbulent kinetic energy and dissipation for 2-dimensional axisymmetric flow by using a finite element package, FIDAP.

The technique for determining velocities and forces of water jet and abrasive water jet with the Laser Transit Anemometer and Piezoelectric …

Experimental Investigation Of The Effects Of Blowing Ratio Parameter On Heat Transfer To A Film-Cooled Flat Plate, Marco R. Valencia

Theses and Dissertations

The effects of blowing ratio on film cooling effectiveness were investigated. Two round-nosed test plates were used. One made of aluminum and the second of corian (low thermal conductivity). Injection at 35 degrees in the downstream direction was studied. Helium was mixed with air to produce a density ratio (coolant to mainstream) of 1.6 and 2.0, while the blowing ratio varied from 0.3 to 2.2. Surface temperature was measured by thin film gages located up to a nondimensional downstream distance X/D of 30. Two injection regimes, weak and strong, were found. In the weak regime, film cooling reduced gage heat …

Runge-Kutta Upwind Multigrid Multi-Block Three-Dimensional Thin Layer Navier-Stokes Solver, Frank E. Cannizzaro

Mechanical & Aerospace Engineering Theses & Dissertations

A state-of-the-art computer code has been developed that incorporates a modified Runge-Kutta time integration scheme, Upwind numerical techniques, Multigrid acceleration, and Multi-block capabilities (RUMM). A three-dimensional thin-layer formulation of the Navier-Stokes equations is employed. For turbulent flow cases, the Baldwin-Lomax algebraic turbulence model is used. Two different upwind techniques are available, van Leer's flux-vector splitting and Roe's flux-difference splitting. Full approximation multigrid plus implicit residual and corrector smoothing were implemented to enhance the rate of convergence. Multi-block capabilities were developed to provide geometric flexibility. This feature allows the developed computer code to accommodate any grid topology or grid configuration with …