Fluid Dynamics Commons^™

Turbulent Plenum Jet-Crossflow Validation Via Subgrid Scale Model Variation And Upstream Forcing Under Dynamic Hybrid Rans-Les, Cole W. Mccallum

Mechanical Engineering Undergraduate Honors Theses

In modern gas turbine design, film cooling has become ubiquitous as a method for limiting heat transfer between high temperature gases post-combustion and the surface of downstream blades. This paper validates the use of various computational fluid dynamics techniques in recreating an experiment measuring adiabatic effectiveness over a surface downstream of a compound-angle N2 plenum jet incident on a turbulent-air boundary layer [1]. To do this, both RANS and Dynamic Hybrid RANS-LES (DHRL) methods are implemented and compared to previous research [2]. The latter method is then modified through implementation of a different subgrid scale (SGS) model and through addition …

Numerical Study Of Nutrient Mixing In Trabecular Bone In Microgravity, Disuse And Normogravity, Sagar Gharti

Doctoral Dissertations and Master's Theses

Mechanical loading is known to regulate bone remodeling by driving interstitial fluid flow which stimulates cells and drives nutrient transport within the trabecular network. In microgravity, the absence of mechanical stimulation or loading suppresses convective flow processes, causing diffusion-driven nutrient mixing and renewal, and accelerated bone loss. This thesis investigates how oscillation frequency and trabecular bone density jointly control nutrient mixing and wall shear stress within trabecular cavities.

A computational fluid dynamics (CFD) framework is developed in STAR-CCM+ using a soft-cap oscillation model that mimics cyclic compression. Three idealized trabecular morphologies are simulated across different frequencies to represent microgravity or …

The Role Of Atmospheric Turbulence On Cloud Droplet Distribution And Droplet Impaction On An Airfoil, Arash Shad, Hashnayne Ahmed, ‪Nadim Zgheib, S. Balachandar, S. A. Sherif

Mechanical Engineering Faculty Publications

We conduct turbulence-informed Euler–Lagrange simulations of droplet-laden flow to examine the effects of atmospheric turbulence on droplet impingement characteristics on a NACA 0012 airfoil. We implement statistical overloading, whereby we inject millions of droplets, ranging in diameter from 1 to 160 microns, upstream of the airfoil at an average streamwise velocity of 120 m/s. Within a fraction of a second, these droplets would have either impinged on the airfoil or continued downstream. While the incoming air flow is maintained uniform, droplet injection is informed by ambient turbulence, affecting both the droplet velocity distribution as well as the size-dependent preferential concentration …

Cfd Analysis Of Hydrodynamic Cavitation Through An Orifice: Influence Of Different Inlet Pressures And Number Of Orifice Holes, Lemthong Chanphavong, Vongsavanh Chanthaboune, Keophousone Phonhalath

ASEAN Journal on Science and Technology for Development

Hydrodynamic cavitation (HC) is considered an energy-efficient process with high potential for utilization in many chemical processes. This study presents a computational fluid dynamics (CFD) analysis of cavitating flow through an orifice with a constant flow area. The Reynolds-Averaged Navier-Stokes (RANS) equations, coupled with turbulence and cavitation models, are employed to capture the complex flow behaviors. The effects of inlet pressures and number of orifice-holes on cavitation behavior are investigated. Result of the numerical simulation is validated with the existing experimental data from the literature. The CFD study revealed that cavitation initiates just behind the inlet edge of the orifice …

Impact Of Weather Systems On Uav Parameters Using Computational Fluid Dynamics, Saif Aljuhaishi, Yaseen K. Al-Timimi, Basim I. Wahab

Karbala International Journal of Modern Science

Since drones cannot fly in any kind of weather, they are not safe for time-sensitive activities. The study examines how the passage of weather systems in Iraq leads to the ban on drone flights, and how these weather conditions impact the aerodynamic forces of the drone. Hourly climate data for the study area were obtained from ECMWF ERA5 and CAMS in NetCDF format for four climate stations (Erbil, Baghdad, Rutbah, and Basrah). A ScanEagle drone was chosen for this study. The Python programming language was used to perform mathematical operations to calculate the ban on drone flights. ArcGIS 10.8 was …

Development Of On-The-Fly Quasi-Steady State Approximation For Chemical Kinetics In Cfd, Abhinav Balamurugan

Doctoral Dissertations and Master's Theses

This study analyzes the feasibility of On-The-Fly Quasi-Steady-State Approximation (OTF-QSSA) application for solving chemical kinetics within Computational Fluid Dynamics (CFD) simulations, aiming to reduce the computational demand of detailed mechanisms. An algorithm that dynamically identifies and designates Quasi-Steady-State (QSS) species at specific grid locations and instances during the simulation was developed. With this information, our method pseudo-delays the advancement of concentrations for these QSS species—effectively setting their rate of concentration change to zero for a set number iteration before updating using the detailed mechanism and thereby omitting the computationally intensive processes typically required for their calculation during those skipped iteration. …

Computational Fluid Dynamics Modeling Of Internal Wave Interactions On Conch Reef, Florida Keys, Megan Miller

All HCAS Student Capstones, Theses, and Dissertations

Internal waves breaking on continental shelves play a significant role in mixing and nutrient delivery to coral reef ecosystems. As internal solitary waves, or solitons, propagate shoreward onto continental slopes, they can become unstable and break into turbulent bores that bring cool, nutrient-rich sub-thermocline water shoreward onto coral reefs. The propagation of turbulent bores generated by internal waves interacting with a complex surface creates high-frequency variabilities in the thermal and nutrient environment of Conch Reef in the Florida Keys, which has been studied previously. Here, I have created a three-dimensional model using ANSYS Fluent Computational Fluid Dynamics (CFD) software to …

Microscale To Mesoscale Modeling Of The Ocean Under Tropical Cyclones: Effects Of Sea Spray And Surfactants On Tropical Cyclone Intensity And Air-Sea Gas Exchange, Breanna Lynn Cain Vanderplow

All HCAS Student Capstones, Theses, and Dissertations

Tropical cyclone intensity prediction remains a challenge despite computational and observational developments because successful intensity forecasting requires implementing a multitude of atmospheric and oceanic processes. Hurricane Maria 2017 and Hurricane Dorian 2019 serve as prime examples of rapidly intensifying storms that devastated communities in the Caribbean. A lack of understanding and parameterization of crucial physics involved in tropical cyclone intensity in existing forecast models may have led to these and other forecasting errors.

Microscale physical processes at the air-sea interface are a major factor in intensification of tropical cyclones that are often unaccounted for in forecasting models since they are …

Modeling Residence Time Distribution Of Chromatographic Perfusion Resin For Large Biopharmaceutical Molecules: A Computational Fluid Dynamic Study, Kevin Vehar

KGI Theses and Dissertations

The need for production processes of large biotherapeutic particles, such as virus-based particles and extracellular vesicles, has risen due to increased demand in the development of vaccinations, gene therapies, and cancer treatments. Liquid chromatography plays a significant role in the purification process and is routinely used with therapeutic protein production. However, performance with larger macromolecules is often inconsistent, and parameter estimation for process development can be extremely time- and resource-intensive. This thesis aimed to utilize advances in computational fluid dynamic (CFD) modeling to generate a first-principle model of the chromatographic process while minimizing model parameter estimation's physical resource demand. Specifically, …

Effects Of Surfactants On The Generation Of Sea Spray During Tropical Cyclones, Breanna L. Vanderplow

All HCAS Student Capstones, Theses, and Dissertations

Despite significant improvement in computational and observational capabilities, predicting intensity and intensification of major tropical cyclones remains a challenge. In 2017 Hurricane Maria intensified to a Category 5 storm within 24 hours, devastating Puerto Rico. In 2019 Hurricane Dorian, predicted to remain tropical storm, unexpectedly intensified into a Category 5 storm and destroyed the Bahamas. The official forecast and computer models were unable to predict rapid intensification of these storms. One possible reason for this is that key physics, including microscale processes at the air-sea interface, are poorly understood and parameterized in existing forecast models.

Under tropical cyclones, the air-sea …

Magnetic Control Of Transport Of Particles And Droplets In Low Reynolds Number Shear Flows, Jie Zhang

Doctoral Dissertations

“Magnetic particles and droplets have been used in a wide range applications including biomedicine, biological analysis and chemical reaction. The manipulation of magnetic microparticles or microdroplets in microscale fluid environments is one of the most critical processes in the systems and platforms based on microfluidic technology. The conventional methods are based on magnetic forces to manipulate magnetic particles or droplets in a viscous fluid.

In contrast to conventional magnetic separation method, several recent experimental and theoretical studies have demonstrated a different way to manipulate magnetic non-spherical particles by using a uniform magnetic field in the microchannel. However, the fundamental mechanism …

A Cfd Study Of Steady Fully Developed Laminar Flow Through A 90-Degree Bend Pipe With A Square Cross-Sectional Area, Subodh Sushant Toraskar

Mechanical & Aerospace Engineering Theses & Dissertations

Fluid flow through a closed curved conduit has always been a topic of extensive research, as it has many practical and industrial applications. The flow is generally characterized by a presence of secondary flow, vortical motions and pressure losses for different flow regimes. These observed irregularities may positively or negatively impact the flow. They are beneficial for cases where mixing of fluids is required, usually observed for multiphase flow regimes or detrimental for cases involving particles in the fluid. There are also instances where a particle-laden fluid transported through the curved pipe was directly related to corrosion- erosion related problems. …

Numerical Investigation Of Drop Impingement On Dry And Wet Surfaces., Yisen Guo

Electronic Theses and Dissertations

In-flight icing due to supercooled large droplets (SLDs) imposes great danger on aviation safety. Because of the large size, SLDs have different characteristics than typical cloud droplets that most icing encounters involve. As a result, SLDs more likely hit the wing surface and move into areas not protected by de-icing devices to form ice, which can lead to loss of lift, increase in drag, altered controllability, and eventually stall and loss of control of the aircraft. The phenomenon of droplet splashing is considered as the most important aspect of the SLD icing accretion problem. Although previous studies have established splashing …

A High Quality, Eulerian 3d Fluid Solver In C++, Lejon Anthony Mcgowan

Computer Science and Software Engineering

Fluids are a part of everyday life, yet are one of the hardest elements to properly render in computer graphics. Water is the most obvious entity when thinking of what a fluid simulation can achieve (and it is indeed the focus of this project), but many other aspects of nature, like fog, clouds, and particle effects. Real-time graphics like video games employ many heuristics to approximate these effects, but large-scale renderers aim to simulate these effects as closely as possible.

In this project, I wish to achieve effects of the latter nature. Using the Eulerian technique of discrete grids, I …

Instrument Design Optimization With Computational Methods, Michael H. Moore

Physics Theses & Dissertations

Using Finite Element Analysis to approximate the solution of differential equations, two different instruments in experimental Hall C at the Thomas Jefferson National Accelerator Facility are analyzed. The time dependence of density fluctuations from the liquid hydrogen (LH2) target used in the Q_weak experiment (2011-2012) are studied with Computational Fluid Dynamics (CFD) and the simulation results compared to data from the experiment. The 2.5 kW liquid hydrogen target was the highest power LH2 target in the world and the first to be designed with CFD at Jefferson Lab. The first complete magnetic field simulation of the Super High Momentum …

A Physics-Based Approach To Modeling Wildland Fire Spread Through Porous Fuel Beds, Tingting Tang

Theses and Dissertations--Mechanical and Aerospace Engineering

Wildfires are becoming increasingly erratic nowadays at least in part because of climate change. CFD (computational fluid dynamics)-based models with the potential of simulating extreme behaviors are gaining increasing attention as a means to predict such behavior in order to aid firefighting efforts. This dissertation describes a wildfire model based on the current understanding of wildfire physics. The model includes physics of turbulence, inhomogeneous porous fuel beds, heat release, ignition, and firebrands. A discrete dynamical system for flow in porous media is derived and incorporated into the subgrid-scale model for synthetic-velocity large-eddy simulation (LES), and a general porosity-permeability model is …

Computational Fluid Dynamics Is Key To Better Flying Aircraft, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Computational Fluid Dynamics (Cfd) Modeling Of A Laboratory Scale Coal Gasifier, Kiel S. Schultheiss

College of Graduate Studies: Theses & Dissertations

Furthering gasification technology is an essential part of advancing clean coal technologies. In order to seek insight into the appropriate operations for the formation of synthetic gas (syngas) a numerical simulation was performed to predict the phenomena of coal gasification in a laboratory scale entrained-flow coal gasifier. The mesh for the model was developed with ICEM CFD software and the chemical and physical phenomena were modeled using the fluid flow solver ANSYS FLUENT. Mesh independence was verified. The model was validated with experimental data from several studies performed on a laboratory scale gasifier.

Systematic examination of the model was performed …