Fluid Dynamics Commons^™

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 …

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 …

Stretching A Surface Having A Layer Of Porous Medium In A Viscous Fluid, M. Sajid, Z. Abbas, N. Ali, T. Javed

Applications and Applied Mathematics: An International Journal (AAM)

The present analysis deals with the steady, incompressible flow of a viscous fluid over a stretching sheet having a layer of porous medium of uniform thickness. The two-dimensional flow equations are derived in a Cartesian coordinate system. The semi-infinite region filled with a viscous fluid is divided into two regions namely, a clear fluid region and a region having a uniform pores. Darcy's law has been used for the flow of fluid in the porous medium region. An exact similar solution of the problem is obtained. The obtained solution is constrained by a relation between the porosity parameter and the …

Strain Rate And Orientation Dependencies Of The Strength Of Single Crystalline Copper Under Compression, Virginie Dupont, Timothy C. Germann

Aerospace Engineering - Daytona Beach

Molecular dynamics (MD) simulations are used to model the compression under uniaxial strain of copper single crystals of different orientations at various temperatures and strain rates. Uniaxial strain is used because of the close resemblance of the resulting stress state with the one behind a shock front, while allowing a control of parameters such as strain rate and temperature to better understand the behavior under complex dynamic shock conditions. Our simulations show that for most orientations, the yield strength of the sample is increased with increasing strain rate. This yield strength is also dependent on the orientation of the sample, …

A Mean Curvature Model For Capillary Flows In Asymmetric Containers And Conduits, Yongkang Chen, Noël Tavan, Mark M. Weislogel

Mechanical and Materials Engineering Faculty Publications and Presentations

Capillarity-driven flows resulting from critical geometric wetting criterion are observed to yield significant shifts of the bulk fluid from one side of the container to the other during "zero gravity" experiments. For wetting fluids, such bulk shift flows consist of advancing and receding menisci sometimes separated by secondary capillary flows such as rivulet-like flows along gaps. Here we study the mean curvature of an advancing meniscus in hopes of approximating a critical boundary condition for fluid dynamics solutions. It is found that the bulk shift flows behave as if the bulk menisci are either “connected” or "disconnected." For the connected …

Hydromagnetic Instability Of Streaming Viscoelastic Fluids Through Porous Media, Pardeep Kumar, Hari Mohan

Applications and Applied Mathematics: An International Journal (AAM)

The hydromagnetic instability of the plane interface between two uniform, superposed and streaming Rivlin-Ericksen viscoelastic fluids through porous medium is considered. The case of two uniform streaming fluids separated by a horizontal boundary is studied. It is observed, for the special case where perturbations in the direction and transverse direction of streaming are ignored, that the system is stable for stable configuration and unstable for unstable configuration. If the perturbations in the direction of streaming only one ignored, then the system is stable for stable configuration. However, the magnetic field succeeds in stabilizing certain wave-number range, which is otherwise potentially …

A Macroscopic Two-Phase Blood Flow Through A Bell Shaped Stenosis In An Artery With Permeable Wall, V. P. Srivastava, Mala Tandon, Rupesh K. Srivastav

Applications and Applied Mathematics: An International Journal (AAM)

The present work concerns the effects of the hematocrit and the permeability of the wall on blood flow characteristics due to the presence of a bell shaped stenosis in an artery. In this analysis, the flowing blood is represented by a macroscopic two-phase model, as a suspension of erythrocytes in plasma. The analytical expressions for the flow characteristics, namely, the flow resistance (impedance), the wall shear stress distribution in the stenotic region and the shearing stress at the stenosis throat have been derived. Results for the effects of permeability as well as of hematocrit on these flow characteristics are shown …

Thermal Instability Of Rivlin-Ericksen Elastico-Viscous Rotating Fluid In Porous Medium In Hydromagnetics, S. K. Kango, Vikram Singh

Applications and Applied Mathematics: An International Journal (AAM)

The thermal instability of a layer of Rivlin-Ericksen elastico-viscous rotating fluid in a porous medium in hydromagnetics is considered. For stationary convection, the Rivlin-Ericksen elastico-viscous fluid behaves like an ordinary (Newtonian) fluid. The magnetic field is found to have a stabilizing effect on the thermal instability of a layer of Rivlin-Ericksen fluid in the absence of rotation whereas the medium permeability has a destabilizing effect on thermal instability of Rivlin-Ericksen fluid in the absence of rotation. Rotation always has a stabilizing effect. The magnetic field, medium permeability and rotation introduce oscillatory modes in the system, which were non-existent in their …

Mhd Mixed Convective Flow Of Viscoelastic And Viscous Fluids In A Vertical Porous Channel, R. Sivaraj, B. R. Kumar, J. Prakash

Applications and Applied Mathematics: An International Journal (AAM)

In this paper, we analyze the problem of steady, mixed convective, laminar flow of two incompressible, electrically conducting and heat absorbing immiscible fluids in a vertical porous channel filled with viscoelastic fluid in one region and viscous fluid in the other region. A uniform magnetic field is applied in the transverse direction, the fluids rise in the channel driven by thermal buoyancy forces associated with thermal radiation. The equations are modeled using the fully developed flow conditions. An exact solution is obtained for the velocity, temperature, skin friction and Nusselt number distributions. The physical interpretation to these expressions is examined …

Superspin Relaxation Times In Fe3o4 / Hexane Magnetic Fluids Measured By Frequency-Resolved Ac Susceptibility, Joshua L. Morris ^, Michael P. Eastman, Cristian E. Botez *

COURI Symposium Abstracts, Spring 2012

A properly formatted abstract has been uploaded below. The pasted version is here

Superspin relaxation times in Fe₃O₄ / hexane magnetic fluids measured by frequency-resolved ac susceptibility

Joshua Morris^ and Cristian E. Botez*

Department of Physics, University of Texas at El Paso, 500 W. University Avenue,

El Paso, TX 79968, U.S.A

Michael P. Eastman

Department of Chemistry, University of Texas at El Paso, 500 W. University Avenue,

El Paso, TX 79968, U.S.A

We have used frequency-resolved (100 Hz < f < 10,000 Hz) ac magnetic susceptibility measurements to directly determine the Néel and Brown relaxation times in 30-nm-size Fe₃O₄ / hexane magnetic fluids at temperatures between 200 and 300 K. Our data collected on both …

Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

The impacts of the two-beam interference heating on the number of core-shell and embedded nanoparticles and on nanostructure coarsening are studied numerically based on the non-linear dynamical model for dewetting of the pulsed-laser irradiated, thin (< 20 nm) metallic bilayers. The model incorporates thermocapillary forces and disjoining pressures, and assumes dewetting from the optically transparent substrate atop of the reflective support layer, which results in the complicated dependence of light reflectivity and absorption on the thicknesses of the layers. Stabilizing thermocapillary effect is due to the local thickness-dependent, steady- state temperature profile in the liquid, which is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Linear stability analysis of the model equations set for Ag/Co bilayer predicts the dewetting length scales in the qualitative agreement with experiment.

Electric-Field-Induced Interfacial Instabilities Of A Soft Elastic Membrane Confined Between Viscous Layers, Mohar Dey, Dipankar Bandyopadhyay, Ashutosh Sharma, Shizhi Qian, Sang Woo Joo

Mechanical & Aerospace Engineering Faculty Publications

We explore the electric-field-induced interfacial instabilities of a trilayer composed of a thin elastic film confined between two viscous layers. A linear stability analysis (LSA) is performed to uncover the growth rate and length scale of the different unstable modes. Application of a normal external electric field on such a configuration can deform the two coupled elastic-viscous interfaces either by an in-phase bending or an antiphase squeezing mode. The bending mode has a long-wave nature, and is present even at a vanishingly small destabilizing field. In contrast, the squeezing mode has finite wave-number characteristics and originates only beyond a threshold …

Microfluidic Impedance Spectroscopy As A Tool For Quantitative Biology And Biotechnology, Ahmet C. Sabuncu, Jie Zhuang, Juergen F. Kolb, Ali Beskok

Mechanical & Aerospace Engineering Faculty Publications

A microfluidic device that is able to perform dielectric spectroscopy is developed. The device consists of a measurement chamber that is 250 μm thick and 750 μm radius. Around 1000 cells fit inside the chamber assuming average quantities for cell radius and volume fraction. This number is about 1000 folds lower than the capacity of conventional fixtures. A T-cell leukemia cell line Jurkat is tested using the microfluidic device. Measurements of deionized water and salt solutions are utilized to determine parasitic effects and geometric capacitance of the device. Physical models, including Maxwell-Wagner mixture and double shell models, are used to …

Microfluidic Separation Of Live And Dead Yeast Cells Using Reservoir-Based Dielectrophoresis, Saurin Patel, Daniel Showers, Pallavi Vedantam, Tzuen-Rong Tzeng, Shizhi Qian, Xiangchun Xuan

Mechanical & Aerospace Engineering Faculty Publications

Separating live and dead cells is critical to the diagnosis of early stage diseases and to the efficacy test of drug screening, etc. This work demonstrates a novel microfluidic approach to dielectrophoretic separation of yeast cells by viability. It exploits the cell dielectrophoresis that is induced by the inherent electric field gradient at the reservoir-microchannel junction to selectively trap dead yeast cells and continuously separate them from live ones right inside the reservoir. This approach is therefore termed reservoir-based dielectrophoresis (rDEP). It has unique advantages as compared to existing dielectrophoretic approaches such as the occupation of zero channel space and …

Flow Over A Traveling Wavy Foil With A Passively Flapping Flat Plate, Nansheng Liu, Yan Peng, Youwen Liang, Xiyun Lu

Mathematics & Statistics Faculty Publications

Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The …

Compound Capillary Rise, Mark M. Weislogel

Mechanical and Materials Engineering Faculty Publications and Presentations

Irregular conduits, complex surfaces, and porous media often manifest more than one geometric wetting condition for spontaneous capillary flows. As a result, different regions of the flow exhibit different rates of flow, all the while sharing common dynamical capillary pressure boundary conditions. The classic problem of sudden capillary rise in tubes with interior corners is revisited from this perspective and solved numerically in the self-similar visco-capillary limit à laLucas–Washburn. Useful closed-form analytical solutions are obtained in asymptotic limits appropriate for many practical flows in conduits containing one or more interior corner. The critically wetted corners imbibe fluid away from …

Electrokinetic Properties Of Lipid And Sarcoplasmic Reticulum Membranes In Aqueous Electrolyte And In The Presence Of Lipophilic Ions, Laura Elizabeth Satterfield

Dissertations and Theses

The purpose of this study is the characterization of the membrane-water interfaces of both sarcoplasmic reticulum membrane (SR) and charged lipid bilayers under varied properties of the surrounding aqueous solution. In this work we studied the electrokinetic properties of liposomes and SR vesicles as well as the interaction of lipophilic ions with these membranes. The study of electrokinetic properties is based on the measurements of electrophoretic mobility of SR membrane vesicles and PC/PG liposomes. Electrophoretic mobility of SR vesicles was measured as a function of ionic strength for six pH values (pH 4.0, 4.7, 5.0, 6.0, 7.5, and 9.0). Electrophoretic …

Unitary Qubit Lattice Gas Representation Of 2d And 3d Quantum Turbulence, George Vahala, Bo Zhang, Jeffrey Yepez, Linda L. Vahala, Min Soe

Electrical & Computer Engineering Faculty Publications

No abstract provided.

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

Mathematical Modeling Of Peristaltic Flow Of Chyme In Small Intestine, Daniel N. Riahi, Ranadhir Roy

Applications and Applied Mathematics: An International Journal (AAM)

Mathematical models based on axisymmetric Newtonian incompressible fluid flow are studied for the peristaltic flow of chyme in the small intestines, which is an axisymmetric cylindrical tube. The flow is modeled more realistically modeled by assuming that the peristaltic rush wave is a non-periodic mode composed of two sinusoidal waves of different wavelengths, which propagate at the same speed along the outer boundary of the tube. Both cases of flow in a tube and in an annulus that are modeled and investigated in the present paper correspond respectively to the cases of flow of chyme in the small intestine in …

The Power Series Solution Of Fingering Phenomenon Arising In Fluid Flow Through Homogeneous Porous Media, Kinjal Patel, M. N. Mehta, Twinkle R. Patel

Applications and Applied Mathematics: An International Journal (AAM)

The present paper deals with the approximate solution of the fingering phenomenon occurring when water is pushed into oil in homogeneous porous media with capillary mean pressure. The phenomenon is formulated mathematically as a water-oil double phase flow problem. The solution of the nonlinear partial differential equation of fingering phenomenon has been discussed in terms of the power series using appropriate boundary conditions for any timeT>0 . The solution is in ascending power series which represents saturation of injected fluid in fingering phenomenon & its graphical and numerical presentation is given in MATLAB coding.

Stability Of Stratified Couple-Stress Dusty Fluid In The Presence Of Magnetic Field Through Porous Medium, Vivek Kumar

Applications and Applied Mathematics: An International Journal (AAM)

The combined effect of magnetic field and dust particles on the stability of a stratified couplestress fluid through a porous medium is considered. For stable stratification, the system is found to be stable for disturbances of all wave numbers. The magnetic field succeeds in stabilizing the potentially unstable stratifications for a certain wave-number range which were unstable in the absence of the magnetic field. Discussions of oscillatory and non-oscillatory modes are also made.

Peristaltic Induced Flow Of A Two-Layered Suspension In Non-Uniform Channel, Amit Medhavi, Dharmendra Singh, Ajay S. Yadav, Ramesh S. Gautam

Applications and Applied Mathematics: An International Journal (AAM)

Peristaltic transport of a two-layered particulate suspension in a non-uniform channel has been investigated. The coupled differential equations for both the fluid and the particle phases in the central as well as in the peripheral layers have been solved and the expression for the flow rate, the pressure rise and the friction force has been derived. The results obtained are discussed both qualitatively and quantitatively in brief. The significance of the particle concentration as well as the peripheral layer has been well explained.

Nonlinear Progressive Wave Equation For Stratified Atmospheres, B. Edward Mcdonald, Andrew A. Piacsek

All Faculty Scholarship for the College of the Sciences

The nonlinear progressive wave equation (NPE) [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is expressed in a form to accommodate changes in the ambient atmospheric density, pressure, and sound speed as the time-stepping computational window moves along a path possibly traversing significant altitude differences (in pressure scale heights). The modification is accomplished by the addition of a stratification term related to that derived in the 1970s for linear range-stepping calculations and later adopted into Khokhlov-Zabolotskaya-Kuznetsov-type nonlinear models. The modified NPE is shown to preserve acoustic energy in a ray tube and yields analytic similarity solutions for …

Left Ventricular Assist Devices: Engineering Design Considerations, Marwan A. Simaan, Eduardo Divo, George Faragallah, Yu Wang

Publications

Patients with end-stage congestive heart failure awaiting heart transplantation often wait long periods of time (300 days or more on the average) before a suitable donor heart becomes available. The medical community has placed increased emphasis on the use of Left Ventricular Assist Devices or LVADs that can substitute for, or enhance, the function of the natural heart while the patient is waiting for the heart transplant (Poirier, 1997; Frazier & Myers, 1999). Essentially, a rotary LVAD is a pump that operates continuously directing blood from the left ventricle into the aorta by avoiding the aortic valve. Generally speaking, the …

Turbulence And Wave Dynamics Across Gas–Liquid Interfaces, Shahrdad Sajjadi, Julian Hunt, Stephen Belcher, Derek Stretch, John Clegg

Publications

Mechanisms are reviewed here for the distortion of turbulent flows near thin density interfaces and their effects on transfer processes across them. Firstly the results of rapid distortion calculations show how the in homogeneous eddy structure depends on whether the turbulence is generated above or below the interface, or in both regions. The flow is unstratified and the buoyancy forces are stable and strong enough relative to the inertial forces that the interface is continuous. It is shown that as the surface blocks the vertical turbulent eddy motions, horizontal straining motions are induced which affect the surface viscous layers and …

Small Reynolds Number Steady Flow Past A Sphere With A Source At Its Centre, Sunil Datta, Shanu Singhal

Applications and Applied Mathematics: An International Journal (AAM)

In this paper we study the steady flow, at low Reynolds number R , past a pervious sphere with a source at its centre. Assuming the source strength s also to be small, we use the method of matched asymptotic expansions to generate the inner and outer solutions pertaining to the problem. Graphs depicting the streamlines have been drawn to exhibit the effects of s and R . Also, the expression of the calculated drag experienced by the sphere shows that the effect of a source (s > o) is to decrease the drag.

Similarity Solution For Flow Of A Micro-Polar Fluid Through A Porous Medium, Kh. S. Mekheimer, R. E. Abo-Elkhair, S. Z. -A. Husseny, A. T. Ali

Applications and Applied Mathematics: An International Journal (AAM)

The equations of two dimensional incompressible steady micro-polar fluid flows through a porous medium are studied. Lie group analysis is employed and the solutions corresponding to the translational symmetry are developed. A boundary value problem is investigated and the results are sketched graphically. The effect on the flow of the porosity coefficient of the porous medium and the micro-polar parameters are observed.

Peristaltic Induced Flow Of A Particulate Suspension In A Non-Uniform Geometry, Amit Medhavi, U. K. Singh

Applications and Applied Mathematics: An International Journal (AAM)

The flow induced by sinusoidal peristaltic waves of a particle-fluid suspension in a twodimensional diverging channel under low Reynolds number and long wavelength approximation has been investigated. The analytical expression for the flow characteristics-the flow rate, pressure rise and friction force have been derived. Moreover, we present some results concerning the dependence of these quantities on the geometrical parameters.

Analysis Of Flow Fields In A Flexible Tube With Periodic Constriction, Swati Mukhopadhyay, Prativa R. De, Mani S. Mandal, G. C. Layek

Applications and Applied Mathematics: An International Journal (AAM)

Numerical techniques based on pressure-velocity formulation have been adopted to solve approximately, the governing equations for viscous flows through a tube (simulating an artery) with a periodic constriction. The effect of the constriction as well as the rigid of the tube, on the flow characteristics, and its consequences for arterial disease is the focus of this investigation. The unsteady incompressible Navier-Stokes equations are solved by using the finite-difference technique in staggered grid distribution. The haemodynamic factors like wall shear stress, pressure and velocity are analyzed through their graphical representations. Maximum resistance is attained in case of rigid stenosed tube rather …