Engineering Commons^™

Turbulence Analysis For The Improvement Of Internal Combustion Engine Efficiency, James R. Macdonald, Claudia Fajardo-Hansford

Research and Creative Activities Poster Day

Developing a complete understanding of the structure and behavior of the near-wall region (NWR) in reciprocating, internal combustion (IC) engines and of its interaction with the core flow is needed to support the implementation of advanced combustion and operating strategies to improve engine efficiency. The NWR in IC engines is fundamentally different from the canonical steady-state turbulent boundary layers (BL), which have been extensively researched. Motivated by this need, this poster presents results from the analysis of two-component velocity data measured with particle image velocimetry near the head of a single-cylinder, optical engine. The interaction between the NWR and the …

An Experimental Investigation Of Wing-Tip Vortex Decay In Turbulence, Hai G. Ghimire, Sean C. C. Bailey

Mechanical Engineering Faculty Publications

Particle image velocimetry measurements were conducted for a wing-tip vortex decaying in free-stream turbulence. The vortex exhibited stochastic collapse with free-stream turbulence present, with the breakdown initiating earlier for higher levels of turbulence. An increased rate of decay of the vortex tangential velocity was also observed, increasing with increasing free-stream turbulence. The decay of the vortex tangential velocity without the free-stream turbulence was well represented by viscous diffusion, resulting in an increase in the core radius and decrease in the peak tangential velocity. With the addition of free-stream turbulence, the rate of decay of the peak tangential velocity of the …

Effects Of Turbulence On The Separating-Reattaching Flow Above Surface-Mounted, Three-Dimensional Bluff Bodies, Abul Fahad Akon

Electronic Thesis and Dissertation Repository

Investigations of separated and reattaching flows over three-dimensional bluff bodies in turbulent boundary layers are important because of the large aerodynamic loads that these flows cause. For example, roofs of low-rise buildings are vulnerable to this kind of wind loading. Turbulence in the upstream flow affects the pressure distributions and the mean size of separation bubbles formed on bluff body surfaces. Whereas a number of studies have focussed on two-dimensional separation bubbles and surface pressures, a comprehensive understanding of the surface pressures and the separating-reattaching flows in relation to the turbulence in the incident boundary layers for surface-mounted, three-dimensional bluff …

Piv Analysis Of Wake Structure Of Real Elephant Seal Whiskers, Joseph Antun Bunjevac

ETD Archive

Seals are able to accurately detect minute disturbances in the ambient flow
environment using their whiskers, which is attributed to the exceptional capability of
their whiskers to suppress vortex-induced vibrations in the wake. To explore potential applications for designing smart flow devices, such as high-sensitivity underwater
flow sensors and drag reduction components, researchers have studied how the role
of some key parameters of whisker-like morphology affect the wake structure. Due to
the naturally presented variation in size and curvature along the length of whiskers,
it is not well understood how a real whisker changes the surrounding flow and the
vortex …

Atmospheric Boundary Layer Processes To Mimic Peak Pressures On Low-Rise Buildings: Cfd Versus Full-Scale And Wind Tunnel Measurements, Hamzeh Gol Zaroudi

LSU Doctoral Dissertations

Realistic prediction of peak wind pressures is indispensable in a safe design of low-rise buildings. For several decades wind tunnel testing was employed to obtain wind loads on buildings and other structures. However, there is still doubt in the wind engineering community regarding the adequacy of wind tunnels to predict accurately full-scale pressures on low-rise buildings and small-size structures. The recommendations of the American Society of Civil Engineers (ASCE) 7-10 standard for external pressure coefficients, for roof components and cladding (C&C) design are also based on published wind tunnel data. Recent field measurements show significant deviation of full-scale pressures from …

Data-Driven Adaptive Reynolds-Averaged Navier-Stokes K - Ω Models For Turbulent Flow-Field Simulations, Zhiyong Li

Theses and Dissertations--Mechanical Engineering

The data-driven adaptive algorithms are explored as a means of increasing the accuracy of Reynolds-averaged turbulence models. This dissertation presents two new data-driven adaptive computational models for simulating turbulent flow, where partial-but-incomplete measurement data is available. These models automatically adjust (i.e., adapts) the closure coefficients of the Reynolds-averaged Navier-Stokes (RANS) k-ω turbulence equations to improve agreement between the simulated flow and a set of prescribed measurement data.

The first approach is the data-driven adaptive RANS k-ω (D-DARK) model. It is validated with three canonical flow geometries: pipe flow, the backward-facing step, and flow around an airfoil. For all 3 test …

Development Of A One-Equation Eddy Viscosity Turbulence Model For Application To Complex Turbulent Flows, Timothy Wray

McKelvey School of Engineering Theses & Dissertations

Computational fluid dynamics (CFD) is routinely used in performance prediction and design of aircraft, turbomachinery, automobiles, and in many other industrial applications. Despite its wide range of use, deficiencies in its prediction accuracy still exist. One critical weakness is the accurate simulation of complex turbulent flows using the Reynolds-Averaged Navier-Stokes equations in conjunction with a turbulence model. The goal of this research has been to develop an eddy viscosity type turbulence model to increase the accuracy of flow simulations for mildly separated flows, flows with rotation and curvature effects, and flows with surface roughness. It is accomplished by developing a …

Turbulence Control In Wall Jets, Jonathan Latim

Doctoral Dissertations and Master's Theses

The turbulent boundary layer has been the focus of many studies over the last century or so due to its engineering significance. Recent studies have shown that the turbulent boundary layer encapsulates extremely energetic large-scale structures which play a much more significant role in its dynamics than has been previously thought. Further, these large scales amplitude and frequency modulate the finer scales of turbulence. This offers a path to control wall turbulence by controlling the large-scales of the flow. The focus of this thesis is to establish ways to manipulate the energy of the large-scale structures in a model turbulent …

Best Practices For Volume Flow Rate Measurements Using Piv At The Exit Of A Turbulent Planar Jet, Rick Cressall

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Particle image velocimetry (PIV) is used to make volume-flow-rate measurements at the exit of a turbulent, planar nozzle. The objective of this report is to assess a range of data acquisition and processing parameters. Data is acquired for volume flow rates of Reynolds numbers between 10,000 and 100,000 for both two-component (2C) and stereo PIV. The parameters are systematically changed one at a time and evaluated using differences in uncertainty, calculation time, and volume- flow-rate deviation. Data acquisition parameters follow the trends of previous work. A multitude of processing parameters were varied for several PIV processing methods. Recommendations for each …

Computational Fluid Dynamics Study Of Molten Steel Flow Patterns And Particle-Wall Interactions Inside A Slide-Gate Nozzle By A Hybrid Turbulent Model, Mahdi Mohammadi-Ghaleni, Mohsen Asle Zaeem, Jeffrey D. Smith, Ronald J. O'Malley

Materials Science and Engineering Faculty Research & Creative Works

Melt flow patterns and turbulence inside a slide-gate throttled submerged entry nozzle (SEN) were studied using Detached–Eddy Simulation (DES) model, which is a combination of Reynolds–Averaged Navier–Stokes (RANS) and Large–Eddy Simulation (LES) models. The DES switching criterion between RANS and LES was investigated to closely reproduce the flow structures of low and high turbulence regions similar to RANS and LES simulations, respectively. The melt flow patterns inside the nozzle were determined by k–ε (a RANS model), LES, and DES turbulent models, and convergence studies were performed to ensure reliability of the results. Results showed that the DES model has significant …

Effect Of Gap Flow On The Shallow Wake Of A Sharp-Edged Bluff Body – Turbulence Parameters, A.M Shinneeb, R. Balachandar

Civil and Environmental Engineering Publications

This experimental study was carried out to investigate the turbulent wake generated by a vertical sharp-edged flat plate suspended in a shallow channel flow with a gap near the bed. The objective of this study is to understand the effect of the gap flow on the turbulent wake by studying two different gap heights between the channel bed and the bottom edge of the bluff body. These two cases were compared to the no-gap case which is considered as a reference case. The maximum flow velocity was 0.45 m/s and the Reynolds number based on the water depthwas 45,000. Extensivemeasurements …

Hydrodynamics And Transverse Mixing In A Rectangular Channel With Bed Forms And Bank Vegetation, M. Ghasemi, M. Heidarpour, C. Gualtieri, S. H. Tabatabaei

International Congress on Environmental Modelling and Software

The analysis of contaminants mixing in natural channels is an important topic of Environmental Hydraulics. In the mid-field, the prediction of transverse mixing is complicated by other typical features of natural channels, such as bed forms and vegetation. The present experimental research investigated the effects of bedforms and banks vegetation on the structure of the turbulent flow field and on the transverse mixing process in a channel. A flume equipped with a set of ten 2D fixed dunes on the bed and rice stems at the banks was used. Detailed velocity measurements were performed using acoustic Doppler velocimetry. Mixing measurements …

Computational Fluid Dynamic Modeling Of Natural Convection In Vertically Heated Rods, Mahesh Surendran

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Natural convection is a phenomenon that occurs in a wide range of applications such as cooling towers, air conditioners, and power plants. Natural convection may be used in decay heat removal systems such as spent fuel casks, where the higher reliability inherent of natural convection is more desirable than forced convection. Passive systems, such as natural convection, may provide better safety, and hence have received much attention recently. Cooling of spent fuel rods is conventionally done using water as the coolant. However, it involves contaminating the water with radiation from the fuel rods. Contamination becomes dangerous and difficult for humans …

Fluidic Jet Turbulence Generators For Deflagration To Detonation Transition In Pulsed Detonation Combustors, Jarrett E. Lowe

Doctoral Dissertations and Master's Theses

The goal of this study is to establish the dominant flow structure required to effectively accelerate the turbulent deflagration flame front to detonation velocity in the shortest possible distance while using a single Jet in Cross Flow (JICF). Jets in crossflow, depending on orientation and momentum ratio, can induce two types of flow structures that propagate downstream; vortex filaments and turbulent eddies. Vortex flow structures are coherent rotating columns that can persist for a considerable distance before diffusing. Turbulent eddies are characterized as random fluctuations in flow velocity or small pockets of rotation. The test rig used for this study …

Experimental Validation Data For Cfd Of Forced Convection On A Vertical Flat Plate, Jeff R. Harris, Blake W. Lance, Barton L. Smith

Mechanical and Aerospace Engineering Faculty Publications

A CFD validation data set for turbulent forced convection on a vertical plate is presented. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions and system response quantities. All important inflow quantities for RANS CFD are also measured. Data are acquired at two heating conditions and cover the range 40;000 < Rex < 300;000, 357 < Red2 < 813 and 0:02 < Gr/Re2 < 0:232. The data and uncertainties are contained in files in the supplemental material

Flame-Turbulence Interaction For Deflagration To Detonation, Jessica Chambers

Honors Undergraduate Theses

Detonation is a high energetic mode of pressure gain combustion that exploits total pressure rise to augment high flow momentum and thermodynamic cycle efficiencies. Detonation is initiated through the Deflagration-to-Detonation Transition (DDT). This process occurs when a deflagrated flame is accelerated through turbulence induction, producing shock-flame interactions that generate violent explosions and a supersonic detonation wave. There is a broad desire to unravel the physical mechanisms of turbulence induced DDT. For the implementation of efficient detonation methods in propulsion and energy applications, it is crucial to understand optimum turbulence conditions for detonation initiation. The study examines the role of turbulence-flame …

Development Of An Unmanned Aerial Vehicle For Atmospheric Turbulence Measurement, Brandon M. Witte

Theses and Dissertations--Mechanical Engineering

An unmanned aerial vehicle was developed to study turbulence in the atmospheric boundary layer. The development of the aircraft, BLUECAT5, and instrumentation package culminated in a series of flight experiments conducted in two different locations near Stillwater, Oklahoma, USA. The flight experiments employed the use of two of the unmanned aerial vehicles flying simultaneously, each containing a five-hole pressure probe as part of a turbulence-measuring instrumentation package. A total of 18 flights were completed with the objective to measure atmospheric properties at five altitudes between 20 and 120 meters. Multiple flights were flown over two days in which the effects …

Numerical Modeling Of Wetland Hydrodynamics, Agnimitro Chakrabarti

LSU Doctoral Dissertations

Wave induced erosion accounts for as much as 26% of landloss in coastal Louisiana. This dissertation work, focuses on answering research questions relevant to the design of two shoreline protection methods (a) vegetated wetlands and (b) nearshore breakwaters. Two types of numerical models are used - the three-dimensional (3D) Navier Stokes Equation for small to medium scale experiments and a depth integrated, fully non-linear Boussinesq model for dispersive waves for larger, field scale studies. The former model provides insights into the 3D hydrodynamics of wave interaction with vegetation canopies and breakwaters, while the latter model focuses on the horizontal two …

An Experimental And Numerical Study Of Surface Interactions In Turbulent Swirling Jets, Zahir Uddin Ahmed

Theses: Doctorates and Masters

Convective heat transfer and drying processes are found in industrial applications from gas turbine blade cooling to drying of food products and paper. In many instances, these processes rely on either a single or an array of fluid jets which impinge onto a surface. Traditionally, non-swirling impinging jets have been used, but interest surrounds possible advantages from imposing swirl into these jets to further promote heat and mass transfer at the surface. The challenge of resolving this question is that including swirl further complicates fluid-surface interactions. Studies are faced with the complexity of flow behaviour, the need for intricate measurement …

Computational Fluid Dynamics (Cfd) Simulations Of Molten Steel Flow Patterns And Particle-Wall Adhesion In Continuous Casting Of Steels, Mahdi Mohammadi-Ghaleni

Masters Theses

"In this research, the measurements of clog deposit thickness on the interior surfaces of a continuous casting nozzle were compared with Computational Fluid Dynamics (CFD) predictions of melt flow patterns and particle-wall interactions to identify the mechanisms of nozzle clogging. A hybrid turbulent approach, Detached Eddy Simulation (DES), was configured to simulate both turbulent structures and particle-wall interactions inside the nozzle accurately. For experimental measurements of nozzle clogging, a nozzle received from industry was encased in epoxy and carefully sectioned to allow measurement of the deposit thickness on the internal surfaces of the nozzle. CFD simulations of melt flow patterns …

Computation Of Hypersonic Flows With Lateral Jets Using K-Ω Turbulence Model, Spatika Dasharati Iyengar

Doctoral Dissertations and Master's Theses

Thermal Protection systems (TPS) are used as shields in space vehicles which encounter high heat and temperatures at the reentry altitudes. Among them, the cooling techniques and the ablative coatings are most popular. However, they have their own weight limitations. In the recent decade, another classification of TPS called the Non-Ablative Thermal Protection systems (NaTPS) have gained significance. The spike-lateral jet method is an NaTPS concept proposed for drag and heat flux reduction in hypersonic nose cones. Numerical simulations are conducted to analyze the effectiveness of spike-lateral jet concept at re-entry altitudes. The spike attached to the hemispherical nose has …

The Three-Dimensional Turbulent Boundary Layer On A Rotating Disk, Daniel Digre

Doctoral Dissertations and Master's Theses

Three-dimensional turbulent boundary layers (3DTBL) are seen quite commonly in nature as well as in the engineering applications. Despite this, very few high Reynolds number studies have been carried out on these boundary layers, particularly focusing on eddy structure, eddy scales and their interactions. The current study focused on developing, characterizing and evaluating an experimental framework to study high Reynolds number #3DTBL on a rotating disk with the long-term goal of carrying out high-fidelity measurements. The rotating disk flow is characterized by weak centrifugal pumping which sets up the cross flow that leads to turbulence. The tangential and radial velocities …

Multiple Scales Of Beach Morphodynamic Processes: Measurements And Modelling, Jun Cheng

USF Tampa Graduate Theses and Dissertations

Multiple scales of beach morphodynamic processes ranging from those of wave-breaking induced turbulence, individual wave, storm, seasonal, to inter-annual are examined in this dissertation based on both laboratory and field data. These processes were simulated using process-based numerical models and data-driven models.

At a microscale, separating turbulence from orbital motion under breaking waves in the surf zone is essential to understanding wave-energy dissipation. Velocity data under monochromatic and random waves in the large-scale sediment transport facility (LSTF) were analyzed. Moving averaging provides a simple method for extracting turbulence from velocity measurements under random breaking waves collected at a reasonably high …

Effect Of Gap Flow On The Shallow Wake Of A Sharp-Edged Bluff Body –Mean Velocity Fields, A.M Shinneeb, R. Balachandar

Civil and Environmental Engineering Publications

This experimental study was carried out to investigate the turbulent shallow wake generated by a vertical sharp-edged flat plate suspended in a shallow channel flow with a gap near the bed. The objective of this study is to understand the effect of the gap flow on the wake by studying two different gap heights between the channel bed and the bottom edge of the bluff body. These two cases will be compared to the no-gap case which is considered as a reference case. Themaximumflowvelocity was 0.45m/s and the Reynolds number based on the water depthwas 45,000. Extensivemeasurements of the flowfield …

Near-Wall Measurements For A Turbulent Impinging Slot Jet System, Jiang Zhe, Vijay Modi

Dr. Jiang Zhe

The velocity field in the vicinity of a target surface with a turbulent slot jet impinging normally on it is examined. The impingement region is confined by means of a confinement plate that is flush with the slot and parallel to the impingement plate. The distance H of the impingement wall from the slot is varied from 2 to 9.2 slot widths. Jet Reynolds numbers (based on slot width B) of 10,000–30,000 are considered. Mean velocity and root mean square velocity measurements are carried out using hot-wire anemometry. A boundary layer probe is utilized in order to obtain measurements at …

Construction Of Naca 66-415 Nlf Composite Wing For Acoustic Turbulence Testing, Scott Sawyer, Sean Stewart

Dr. Scott Sawyer

A design is developed for a Natural Laminar Flow (NLF) wing, to be used at California Polytechnic State University for acoustic turbulence testing. Composite materials are used to produce high-quality surface finishes necessary for laminar flow. A design for the test apparatus is presented and justified. A manufacturing procedure is proposed for the carbon fiber skin, using Vacuum Resin Infusion (VRI). This procedure is tested on a scaled part with satisfactory results; lessons learned are discovered and integrated into the final manufacturing process. The test section has been fit to the Cal Poly wind tunnel, but full implementation has not …

An Examination Of The Potential For Distributed Wind Generation (Dwg) In Urban Distribution Networks, Keith Sunderland, Thomas Woolmington, Michael Conlon, Gerald Mills

Conference papers

In a sustainable economy, smarter cities need energy networks that can deliver consistent electricity while maximising the use of intermittent renewables. Therefore an understanding of the available resource and a means for viable integration of distributed generation (DG) is required. In this research, energy harvesting of the wind climate is considered in the context of distributed wind generation (DwG) as an integral component of a smarter electricity network. The approach combines wind climate modeling of the resource at the urban scale with enhanced electricity network simulation. The former considers energy harvesting potential while the latter investigates the opportunities for this …

Ambit Of Multiphase Cfd In Modelling Transport Processes Related To Oil Spill Scenario And Microfluidics, Abhijit Rao

LSU Doctoral Dissertations

During the ‘Deepwater Horizon’ accident in the deep sea in 2010, about 4.9 million barrels of oil was released into the Gulf of Mexico, making the spill one of the worst ocean spills in recent times. To mitigate the ill effects of the event on the environment, subsea injection of dispersants was carried out. Dispersant addition lowers the interfacial tension at oil/water interface and presence of local turbulence enhances the droplet disintegration process. The oil droplets contain a plethora of hydrocarbons which are soluble in water. In deep spill scenarios, droplets spend large amounts of time in water column; hence, …

Design Of A High Intensity Turbulent Combustion System, Mohammad Arif Hossain

Open Access Theses & Dissertations

In order to design next generation gas turbine combustor and rocket engines, a systematic study of flame structure at high intensity turbulent flow is necessary. The fundamental study of turbulent premixed combustion has been a major research concern for decades. The work is focused on the design and development of a high intensity turbulent combustion system which can be operated at compressible (0.3 < M < 0.5), preheated (T0=500K) and premixed conditions in order to investigate the 'Thickened Flame' regime. An air-methane mixture has been used as the fuel for this study. An optically accessible backward-facing step stabilized combustor has been designed for a maximum operating pressure of 6 bar. A grid has been introduced with different blockage ratios (BR = 54%, 61% & 67%) in order to generate turbulence inside the combustor for the experiment. Optical access is provided via quartz windows on three sides of the combustion chamber. Finite Element Analysis (FEA) is done in order to verify the structural integrity of the combustor at rated conditions. In order to increase the inlet temperature of the air, a heating section was designed to use commercially available in-line heaters. Separate cooling subsystems have been designed for chamber cooling and exhaust cooling. The LabVIEW software interface has been selected as the control mechanism for the experimental setup. A 10 kHz Time Resolved Particle Image Velocimetry (TR-PIV) system and a 3 kHz Planer Laser Induced Fluorescence (PLIF) system have been integrated with the system in order to diagnose the flow field and the flame respectively. The primary understanding of the flow field inside the combustor was achieved through the use of Detached Eddy Simulation (DES) by using commercially available software package ANSYS FLUENT. Preliminary validation is done by 10 kHz TR-PIV technique. Both qualitative and quantitative analysis have been done for CFD and experiment. Major flow parameters such as average velocity, fluctuation of velocity, kinetic energy, and turbulent intensity have been calculated for two distinct Reynolds number (Re = 815 & 3500). PIV results are compared with CFD results which show significant agreement with each other.

Experimental Investigation Of Wall Shear Stress Modifications Due To Turbulent Flow Over An Ablative Thermal Protection System Analog Surface, Jacob Helvey

Theses and Dissertations--Mechanical Engineering

Modifications were made to the turbulent channel flow facility to allow for fully developed rough quasi-2D Poiseuille flow with flow injection through one surface and flow suction through the opposing surface. The combination of roughness and flow injection is designed to be analogous to the flow field over a thermal protection system which produces ablative pyrolysis gases during ablation. It was found that the additional momentum through the surface acted to reduce skin friction to a point below smooth-wall behavior. This effect was less significant with increasing Reynolds number. It was also found that the momentum injection modified the wake …