Fluid Dynamics Commons^™

Gravity Wave Breaking Over Northern Utah With An Advanced Mesospheric Temperature Mapper And Sodium Lidar, Eric Davis

All Graduate Reports and Creative Projects, Fall 2023 to Present

Considerable progress has been made in recent decades in the understanding of gravity wave (GW) dynamics. However, there remain important aspects and effects that are poorly understood. In particular, the coupling and deposition of their energy and momentum into the mesosphere lower thermosphere (MLT) region and the interaction and instability dynamics that are directly associated with GW breaking. Using an Advanced Mesosphere Temperature Mapper (AMTM) several strong wave breaking events were observed in the summer of 2015 at USU’s BLO research station. These events have exhibited high momentum fluxes and associated strong wave breaking, prompting detailed data analyses. Rossby waves, …

Three-Dimensional Spreading Of Magnetic Reconnection Between Non-Parallel Flux Ropes With A Guide Field, Regis John

Graduate Theses, Dissertations, and Problem Reports (ETD)

Magnetic reconnection is a fundamental plasma process that facilitates the rapid conversion of magnetic energy into particle acceleration, plasma flows, and heating. It plays a central role in explosive astrophysical events such as solar flares, where vast amounts of magnetic energy are released on short time scales. A key structure in many reconnection sites is the magnetic flux rope, a column of plasma carrying current threaded by helical magnetic fields, which is frequently involved in or generated by reconnection. Understanding how reconnection unfolds in such flux rope systems is critical for interpreting both space weather phenomena and laboratory plasma dynamics. …

On The Ubiquity, Properties And Evolution Of Small-Scale Magnetic Flux Ropes In The Heliosphere, Hameedullah Farooki

Dissertations

The solar wind is a plasma constantly blowing out from the Sun with a large-scale magnetic field having significant local complexity at small scales. Small-scale magnetic flux ropes (SMFRs), plasma structures with twisted field lines, are an important element of this complexity. This dissertation contributes several studies that further our understanding of SMFRs. The first study applies machine learning to measurements from Wind labeled by the presence of SMFRs and magnetic clouds (MCs). MCs were distinguished from non-MFRs with an AUC of 94% and SMFRs with an AUC of 89% and had distinctive plasma properties, whereas SMFRs appeared to be …

1d Fluid Model Of Rf-Excited Cold Atmospheric Plasmas In Helium With Air Gas Impurities, Yifan Liu, Dingxin Liu, Jishen Zhang, Bowen Sun, Aijun Yang, Michael G. Kong

Bioelectrics Publications

Cold atmospheric plasmas (CAPs) in helium with air gas impurities (HeþAir for abbreviation) compromise the discharge stability of helium and the chemical reactivity of air, having great prospects for various applications such as plasma biomedicine. However, different kinds of reactive species are produced in HeþAir CAPs but only a few of them could be measured, and the plasma chemistry is so complex that the reported simulation models are simplified to a large extent, such as neglecting the space variation of CAPs by using a 0D model. As a result, much remains unknown for HeþAir CAPs, which hinders the development of …

Comparison Between The Water Activation Effects By Pulsed And Sinusoidal Helium Plasma Jets, Han Xu, Dingxin Liu, Wenjie Xia, Chen Chen, Weitao Wang, Zhijie Liu, Xiaohua Wang, Michael G. Kong

Bioelectrics Publications

Comparisons between pulsed and sinusoidal plasma jets have been extensively reported for the discharge characteristics and gaseous reactive species, but rarely for the aqueous reactive species in water solutions treated by the two types of plasma jets. This motivates us to compare the concentrations of aqueous reactive species induced by a pulsed and a sinusoidal plasma jet, since it is widely reported that these aqueous reactive species play a crucial role in various plasma biomedical applications. Experimental results show that the aqueous H₂O₂, OH/O₂⁻, and O₂⁻/ONOO⁻ induced by the …

Production And Correlation Of Reactive Oxygen And Nitrogen Species In Gas- And Liquid-Phase Generated By Helium Plasma Jets Under Different Pulse Widths, Zhijie Liu, Chunxi Zhou, Dingxin Liu, Dehui Xu, Wenjie Xia, Qingjie Cui, Bingchuan Wang, Michael G. Kong

Bioelectrics Publications

In this paper, we present the effects of the pulse width (PW) on the plasma jet's discharge characteristics, particularly focusing on the production and correlation of the reactive oxygen and nitrogen species (RONS) in gas- and liquid-phase. It is found that the length of plasma jet plume first increases before the PW of 10 μs, then gradually decreases and finally almost remains unchanged beyond 150 μs. The plasma bullet disappears after the falling edge of the voltage pulse at low PW, while it terminates far ahead of the falling edge of voltage pulse at high PW. This is …

Nonlinear Waves, Instabilities And Singularities In Plasma And Hydrodynamics, Denis Albertovich Silantyev

Mathematics & Statistics ETDs

This work concentrates on Langmuir wave filamentation instability in the kinetic regime of plasma and computation of Stokes wave with high precision using conformal maps.

Nonlinear effects are present in almost every area of science as soon as one tries to go beyond the first order approximation. In particular, nonlinear waves emerge in such areas as hydrodynamics, nonlinear optics, plasma physics, quantum physics, etc. The results of this work are related to nonlinear waves in two areas, plasma physics and hydrodynamics, united by concepts of instability, singularity and advanced numerical methods used for their investigation.

The first part of this …

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 …

Effects Of Forcing Time Scale On The Simulated Turbulent Flows And Turbulent Collision Statistics Of Inertial Particles, B. Rosa, H. Parishani, O. Ayala, L.-P. Wang

Engineering Technology Faculty Publications

In this paper, we study systematically the effects of forcing time scale in the large-scale stochastic forcing scheme of Eswaran and Pope ["An examination of forcing in direct numerical simulations of turbulence," Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynolds …

Effects Of Gravity On The Acceleration And Pair Statistics Of Inertial Particles In Homogeneous Isotropic Turbulence, H. Parishani, O. Ayala, B. Rosa, L.-P. Wang, W. W. Grabowski

Engineering Technology Faculty Publications

Within the context of heavy particles suspended in a turbulent airflow, we study the effects of gravity on acceleration statistics and radial relative velocity (RRV) of inertial particles. The turbulent flow is simulated by direct numerical simulation (DNS) on a 256³ grid and the dynamics of O(10⁶) inertial particles by the point-particle approach. For particles/droplets with radius from 10 to 60 µm, we found that the gravity plays an important role in particle acceleration statistics: (a) a peak value of particle acceleration variance appears in both the horizontal and vertical directions at a particle Stokes number …

Particle Swarms In Confining Geometries, Eric Robert Boomsma

Open Access Dissertations

The transport of micro- and nano-particles in subsurface fluid deposits is an area of increasing interest due to the rising use of these particles for consumer and industrial purposes. Subsurface particle transport is complicated by the presence of fractures and fracture networks which govern the paths that particles will be able to take. In this thesis, subsurface particle transport will be investigated using particle swarms; collections of hydro-dynamically interacting particles which exhibit group behavior. The effects of fluid viscosity, particle properties, fracture geometry, and fracture aperture on swarm behavior were experimentally investigated. ^ Swarm parameters were examined in time with …

Study Of A Generalized Empirical Model For Predicting Pressure Drop For Internal Flows, Tejas Anup Pant

Open Access Theses

A generalized empirical model for estimating the pressure drop across a channel for a given massflow rate is studied through computational fluid dynamics (CFD) simulations. It is observed that for developing laminar and turbulent flow through channels and pipes of arbitrary cross-section, the variation in the pressure drop between any two points in the flow direction with massflow rate can be well approximated by a second degree expression in massflow rate which is referred to as the empirical model in this study. In the first part of this study, a correlation between the pressure gradient and the massflow rate is …

Special Issue On Plenary And Invited Papers From Icops 2012, Felipe Iza, Carl Ekdahl, Michael G. Kong

Electrical & Computer Engineering Faculty Publications

The 39th International Conference on Plasma Science (ICOPS) was held in Edinburgh, Scotland in July 2012. This was the third time that the conference was organized outside North America, the previous ones being in Karlsruhe (Germany) in 2008 and Jeju (S. Korea) in 2003. The technical programme combined seven technical areas of plasma science and technology covering a wide range of topics. The conference featured a wide range of advances in innovative plasma and beam science and applications, and served as a venue for an international community to meet and discuss their ideas and research results. More than 800 abstracts …

Accelerated Lattice Boltzmann Method For Colloidal Suspensions Rheology And Interface Morphology, Hassan Farhat

Wayne State University Dissertations

ABSTRACT

ACCELERATED LATTICE BOLTZMANN MODEL FOR COLLOIDAL SUSPENSIONS RHEOLOGY AND INTERFACE MORPHOLOGY

by

HASSAN FARHAT

July 2010

Advisor: Dr. Singh Trilochan

Co-Advisor: Dr. Joon Sang Lee

Major: Mechanical Engineering

Degree: Doctor of Philosophy

Colloids are ubiquitous in the food, medical, cosmetic, polymer, water purification and pharmaceutical industries. Colloids thermal, mechanical and storage properties are highly dependent on their interface morphology and their rheological behavior.

Numerical methods provide a cheap and reliable virtual laboratory for the study of colloids. However efficiency is a major concern to address when using numerical methods for practical applications.

This work introduces the main building-blocks for …

Generation Of Mie Size Microdroplet Aerosols With Applications In Laser-Driven Fusion Experiments, Andrew P. Higginbotham '09, O. Semonin '06, S. Bruce '08, C. Chan '08, M. Maindi '07, Thomas D. Donnelly, M. Maurer, W. Bang, I. Churina, J. Osterholz, I. Kim, A. C. Bernstein, T. Ditmire

All HMC Faculty Publications and Research

We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti:Al₂O₃ laser focused to 2×10¹⁹ W/cm² was used to irradiate heavy water (D₂O) aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2×10³ fusion neutrons measured per joule of incident laser energy.

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this thesis is to investigate whether it is feasible to use Langmuir probes on pico-satellites flying in low Earth orbit over mid- to low-latitude geographic regions. Following chapters on the expected ionospheric conditions and an overview of Langmuir probe theory, a chapter addressing the difficulties involved with pico-satellite Langmuir probes is presented. Also, the necessary satellite-to-probe surface area requirements in order to achieve confidence in pico-satellite Langmuir probe data, for the orbital regions of interest to this thesis, are stated.

Self-Organization In Cathode Boundary Layer Discharges, Nobuhiko Takano

Electrical & Computer Engineering Theses & Dissertations

Cathode boundary layer (CBL) discharge, which has been developed as a UV light source, operates in a direct current between a planar cathode and a ring-shape anode that are separated by a dielectric with an opening of the same diameter as the anode. The nonthermal CBL discharges operate in a medium pressure range down to 30 Torr, emitting excimer radiation when operated with noble gases. The radiant excimer emittance at 172 nm in xenon reaches 1.7 W/cm², and a maximum excimer efficiency of 6 % has been obtained. The high excimer radiant emittance, in addition to low cost …

Scaling And Characterization Of Direct Current Glow Discharge Plasma In Atmospheric Air, Abdel-Aleam Hefney Mohamed

Electrical & Computer Engineering Theses & Dissertations

A microhollow cathode discharge was used as a plasma cathode to sustain a stable direct current glow discharge in atmospheric pressure air. The volumetric scale of glow discharge increased from the millimeter to the centimeter range by extending the plasma in lateral and axial directions. In the axial direction, the length of the glow discharge column was varied from 1 mm to 2 cm, with the sustaining voltage increasing linearly with the glow discharge column length. Extension in the lateral direction was obtained by operating discharges in parallel. The glow discharge plasma of the parallel discharge columns was found to …

Microdischarge Arrays, Wenhui Shi

Electrical & Computer Engineering Theses & Dissertations

Microhollow cathode discharges (MHCDs) are DC or pulsed gas discharges between two electrodes, separated by a dielectric, and containing a concentric hole. The diameter of the hole, in this hollow cathode configuration, is in the hundred-micrometer range. MHCDs satisfy the two conditions necessary for an efficient excimer radiation sources: (1) high energy electrons which are required to provide a high concentration of excited or ionized rare gas atoms; (2) high pressure operation which favors excimer formation (a three-body process). Flat panel excimer sources require parallel operation of MHCDs. Based on the current-voltage characteristics of MHCD discharges, which have positive slopes …

Decomposition Of Carbon Dioxide In A Capacitively Coupled Radio Frequency Discharge, Thao Hoang Dinh

Physics Theses & Dissertations

Decomposition of CO₂ was studied in a capacitively coupled radio frequency discharge using Martian Simulant Gas mixture that contains 95% CO₂. The discharge was operated at a gas pressure of 3 to 6 Torr and a discharge power density of less than 2.0 W/cm³. The main mechanism of the CO₂ decomposition process is the electron impact dissociation and the rate of the process depends on the electron density, Ne, the concentration of CO₂, and the reduced electric field, E/N. A self-consistent model was established to describe the CO …

Steady Incompressible Magnetohydrodynamic Flow Near A Point Of Reattachment, J. M. Dorrepaal, S. Moosavizadeh

Mathematics & Statistics Faculty Publications

The oblique stagnation-point flow of an electrically conducting fluid in the presence of a magnetic field is a highly nonlinear problem whose solution is of interest even in the simplest of geometries. The problem models the flow of a viscous conducting fluid near a point where a separation vortex reattaches itself to a rigid boundary. A similarity solution exists which reduces the problem to a coupled system of four ordinary differential equations which can be integrated numerically. The problem has two independent parameters, the conductivity of the fluid and the strength of the magnetic field. Solutions are tabulated for a …

The Effect Of Three-Dimensional Freestream Disturbances On The Supersonic Flow Past A Wedge, Peter W. Duck, D. Glenn Lasseigne, M. Y. Hussaini

Mathematics & Statistics Faculty Publications

The interaction between a shock wave (attached to a wedge) and small amplitude, three-dimensional disturbances of a uniform, supersonic, freestream flow are investigated. The paper extends the two-dimensional study of Duck et al. [P W. Duck, D. G. Lasseigne, and M. Y. Hussaini, ''On the interaction between the shock wave attached to a wedge and freestream disturbances,'' Theor. Comput. Fluid Dyn. 7, 119 (1995) (also ICASE Report No. 93-61)] through the use of vector potentials, which render the problem tractable by the same techniques as in the two-dimensional case, in particular by expansion of the solution by means of …

The Stability Of Compressible Mixing Layers In Binary Gases, F. Kozusko, D. G. Lasseigne, C. E. Grosch, T. L. Jackson

Mathematics & Statistics Faculty Publications

We present the results of a study of the inviscid two-dimensional spatial stability of a parallel compressible mixing layer in a binary gas. The parameters of this study are the Mach number of the fast stream, the ratio of the velocity of the slow stream to that of the fast stream, the ratio of the temperatures, the composition of the gas in the slow stream and in the fast stream, and the frequency of the disturbance wave. The ratio of the molecular weight of the slow stream to that of the fast stream is found to be an important quantity …

Tabletop X-Ray Lasers, D. C. Eder, P. Amendt, L. B. Dasilva, R. A. London, B. J. Macgowan, D. L. Matthews, B. M. Penetrante, M. D. Rosen, S. C. Silks, Thomas D. Donnelly, R. W. Falcone, G. L. Strobel

All HMC Faculty Publications and Research

Details of schemes for two tabletop size x‐ray lasers that require a high‐intensity short‐pulse driving laser are discussed. The first is based on rapid recombination following optical‐field ionization. Analytical and numerical calculations of the output properties are presented. Propagation in the confocal geometry is discussed and a solution for x‐ray lasing in Li‐like N at 247 Å is described. Since the calculated gain coefficient depends strongly on the electron temperature, the methods of calculating electron heating following field ionization are discussed. Recent experiments aimed at demonstrating lasing in H‐like Li at 135 Å are discussed along with modeling results. The …

Absolute-Convective Instabilities And Their Associated Wave Packets In A Compressible Reacting Mixing Layer, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

In this paper the transition from convective to absolute instability in a reacting compressible mixing layer with finite rate chemistry is examined. The reaction is assumed to be one step, irreversible, and of Arrhenius type. It is shown that absolute instability can exist for moderate heat release without backflow. The effects of the temperature ratio, heat release parameter, Zeldovich number, equivalence ratio, direction of propagation of the disturbances, and the Mach number on the transition value of the velocity ratio are given. The present results are compared to those obtained from the flame sheet model for the temperature using the …

A Numerical Study Of Wave Propagation In A Confined Mixing Layer By Eigenfunction Expansions, Fang Q. Hu

Mathematics & Statistics Faculty Publications

It is well known that the growth rate of instability waves of a two-dimensional free shear layer is reduced greatly at supersonic convective Mach numbers. In previous works, it has been shown that new wave modes exist when the shear layers are bounded by a channel due to the coupling effect between the acoustic wave modes and the motion of the mixing layer. The present work studies the simultaneous propagation of multiple stability waves using numerical simulation. It is shown here that the coexistence of two wave modes in the flow field can lead to an oscillatory growth of disturbance …

Induced Mach Wave-Flame Interactions In Laminar Supersonic Fuel Jets, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

A model problem is proposed to investigate the steady response of a reacting, compressible laminar jet to Mach waves generated by wavy walls in a channel of finite width. The model consists of a two-dimensional jet of fuel emerging into a stream of oxidizer which are allowed to mix and react in the presence of the Mach waves. The governing equations are taken to be the steady parabolized Navier-Stokes equations which are solved numerically. The kinetics is assumed to be a one-step, irreversible reaction of the Arrhenius type. Two important questions on the Mach wave-flame interactions are discussed: (i) how …

Erratum: "Temperature And Suction Effects On The Instability Of An Infinite Swept Attachment Line" [Physics Of Fluids A 4, 2008 (1992)], D. G. Lasseigne, T. L. Jackson, F. Q. Hu

Mathematics & Statistics Faculty Publications

Erratum to:

Lasseigne, D. G., Jackson, T. L., & Hu, F. Q. (1992). Temperature and suction effects on the instability of an infinite swept attachment line. Physics of Fluids A: Fluid Dynamics, 4(9), 2008-2012. doi:10.1063/1.858370

Temperature And Suction Effects On The Instability Of An Infinite Swept Attachment Line, D. G. Lasseigne, T. L. Jackson, F. Q. Hu

Mathematics & Statistics Faculty Publications

It is known that the incompressible, infinite swept attachment line flow is unstable to streamwise disturbances that originate in the boundary layer when the cross-flow exceeds a critical magnitude. Furthermore, a small degree of suction at the surface has a significant stabilizing influence while a small degree of blowing has a considerable destabilizing influence. This paper investigates the stabilizing and destabilizing effects of, respectively, cooling or heating the plate and the competing or enhancing effects of suction or blowing. A nonorthogonal flow with respect to the attachment line is also considered by adding a component of shear to the mean …

Parametric Instability Of Supersonic Shear Layers Induced By Periodic Mach Waves, Fang Q. Hu, Christopher K. W. Tam

Mathematics & Statistics Faculty Publications

It is suggested that parametric instability can be induced in a confined supersonic shear layer by the use of a periodic Mach wave system generated by a wavy wall. The existence of such an instability solution is demonstrated computationally by solving the Floquet system of equations. The solution is constructed by means of a Fourier-Chebyshev expansion. Numerical convergence is assured by using a very large number of Fourier and Chebyshev basis functions. The computed growth rate of the induced flow instability is found to vary linearly with the amplitude of the mach waves when the amplitude is not excessively large. …