A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, 2019 Iowa State University and Ames Laboratory

#### A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox

*Alberto Passalacqua*

A computational algorithm for polydisperse bubbly flow is developed by combining quadrature-based moment methods (QBMM) with an existing two-fluid solver for gas–liquid flows. Care is taken to ensure that the two-fluid model equations are hyperbolic by generalizing the kinetic model for the bubble phase proposed by Bieseuvel and Gorissen (1990). The kinetic formulation for the bubble phase includes the full suite of interphase momentum exchange terms for bubbly flow, as well as ad hoc bubble–bubble interaction terms to model the transition from isolated bubbles to regions of pure air at very high bubble-phase volume fractions. A robust numerical ...

A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, 2019 Iowa State University and Ames Laboratory

#### A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox

*Rodney O. Fox*

A computational algorithm for polydisperse bubbly flow is developed by combining quadrature-based moment methods (QBMM) with an existing two-fluid solver for gas–liquid flows. Care is taken to ensure that the two-fluid model equations are hyperbolic by generalizing the kinetic model for the bubble phase proposed by Bieseuvel and Gorissen (1990). The kinetic formulation for the bubble phase includes the full suite of interphase momentum exchange terms for bubbly flow, as well as ad hoc bubble–bubble interaction terms to model the transition from isolated bubbles to regions of pure air at very high bubble-phase volume fractions. A robust numerical ...

A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, 2019 Iowa State University and Ames Laboratory

#### A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox

*Chemical and Biological Engineering Publications*

A computational algorithm for polydisperse bubbly flow is developed by combining quadrature-based moment methods (QBMM) with an existing two-fluid solver for gas–liquid flows. Care is taken to ensure that the two-fluid model equations are hyperbolic by generalizing the kinetic model for the bubble phase proposed by Bieseuvel and Gorissen (1990). The kinetic formulation for the bubble phase includes the full suite of interphase momentum exchange terms for bubbly flow, as well as ad hoc bubble–bubble interaction terms to model the transition from isolated bubbles to regions of pure air at very high bubble-phase volume fractions. A robust numerical ...

Fluid Transport In Porous Media For Engineering Applications, 2019 University of New Mexico

#### Fluid Transport In Porous Media For Engineering Applications, Eric M. Benner

*Chemical and Biological Engineering ETDs*

This doctoral dissertation presents three topics in modeling fluid transport through porous media used in engineering applications. The results provide insights into the design of fuel cell components, catalyst and drug delivery particles, and aluminum- based materials. Analytical and computational methods are utilized for the modeling of the systems of interest. Theoretical analysis of capillary-driven transport in porous media show that both geometric and evaporation effects significantly change the time dependent behavior of liquid imbibition and give a steady state flux into the medium. The evaporation–capillary number is significant in determining the time-dependent behavior of capillary flows in porous ...

High Resolution Validation Of Next Generation Turbulent Flow Models Using Neutron Beams, Laser Fluorescence, And Cryogenic Helium, 2019 University of Tennessee, Knoxville

#### High Resolution Validation Of Next Generation Turbulent Flow Models Using Neutron Beams, Laser Fluorescence, And Cryogenic Helium, Landen G Mcdonald

*EURēCA: Exhibition of Undergraduate Research and Creative Achievement*

Turbulent fluid flow is an incredibly unpredictable subject that continues to confound scientists and engineers. All of the empirical data that has been the basis of conventional turbulent computational fluid dynamics (CFD) models for decades only extends to roughly the equivalent turbulence created when Michael Phelps swims in a pool. The problem is that this data is then extrapolated out many orders of magnitude in order to design cruise ships, airplanes, and rockets which operate in significantly more turbulent flow regimes. This creates an incredible degree of uncertainty in the design process that demands over-engineering and increased expenditures.

The development ...

Modeling Multiphase Flow And Substrate Deformation In Nanoimprint Manufacturing Systems, 2019 University of New Mexico

#### Modeling Multiphase Flow And Substrate Deformation In Nanoimprint Manufacturing Systems, Andrew Cochrane

*Nanoscience and Microsystems ETDs*

Nanopatterns found in nature demonstrate that macroscopic properties of a surface are tied to its nano-scale structure. Tailoring the nanostructure allows those macroscopic surface properties to be engineered. However, a capability-gap in manufacturing technology inhibits mass-production of nanotechnologies based on simple, nanometer-scale surface patterns. This gap represents an opportunity for research and development of nanoimprint lithography (NIL) processes. NIL is a process for replicating patterns by imprinting a fluid layer with a solid, nano-patterned template, after which ultraviolet cure solidifies the fluid resulting in a nano-patterned surface. Although NIL has been demonstrated to replicate pattern features as small as 4 ...

Implementation Of Fast Hydraulic Erosion Simulation And Visualization On Gpu, 2019 University of Nebraska at Omaha

#### Implementation Of Fast Hydraulic Erosion Simulation And Visualization On Gpu, Brian Hawkins

*Computer Science Graduate Research Workshop*

No abstract provided.

Dispersive Hydrodynamics In Viscous Fluid Conduits, 2019 University of Colorado, Boulder

#### Dispersive Hydrodynamics In Viscous Fluid Conduits, Michelle Maiden

*Applied Mathematics Graduate Theses & Dissertations*

Viscous fluid conduits provide an ideal system for the study of dissipationless, dispersive hydrodynamics. A dense, viscous fluid serves as the background medium through which a lighter, less viscous fluid buoyantly rises. If the interior fluid is continuously injected, a deformable pipe forms. The long wave interfacial dynamics are well-described by a dispersive nonlinear partial differential equation called the conduit equation.

Experiments, numerics, and asymptotics of the viscous fluid conduit system will be presented. Structures at multiple length scales are characterized, including solitary waves, periodic waves, and dispersive shock waves. A more generic class of large-scale disturbances is also studied ...

Quantification Of Contrast-Enhanced Ultrasound, 2019 College of Saint Benedict/Saint John's University

#### Quantification Of Contrast-Enhanced Ultrasound, Joseph Pathoulas

*All College Thesis Program, 2016-present*

The aim of this experiment was to investigate the effect of manipulating ultrasound scanner settings on time-intensity curve parameters in a tube perfusion phantom system using contrast-enhanced ultrasound imaging. Imaging was performed using a Philips LOGIQ E9 ultrasound scanner equipped with a C1-6VN transducer and utilized two different microbubble contrast agents: Definity and Lumason. The ultrasound scanner settings manipulated included: gain, dynamic range, and frequency. Additionally, relative microbubble concentration, microbubble type, and perfusion flow rate were manipulated. Four time-intensity curve parameters (time to peak, area under curve, gradient, peak intensity) were measured from linearized pixel data. Time to peak was ...

Capillary Migration Of Large Confined Drops In Non-Wetting Wedges, 2019 Portland State University

#### Capillary Migration Of Large Confined Drops In Non-Wetting Wedges, Logan John Torres

*Dissertations and Theses*

When confined within containers or conduits, drops and bubbles migrate to regions of minimum energy by the combined effects of surface tension, surface wetting, system geometry, and initial conditions. Such capillary phenomena are exploited for passive phase separation operations in micro-fluidic devices on earth and macro-fluidic devices aboard spacecraft. Our study focuses on the migration and ejection of large inertial-capillary drops confined between tilted planar hydrophobic substrates. In our experiments, the brief nearly weightless environment of a drop tower allows for the study of such capillary dominated behavior for up to 10 mL water drops with migration velocities up to ...

Quantifying Uncertainty Of Ensemble Transport And Dispersion Simulations Using Hysplit, 2019 Air Force Institute of Technology

#### Quantifying Uncertainty Of Ensemble Transport And Dispersion Simulations Using Hysplit, Daniel W. Bazemore

*Theses and Dissertations*

Uncertainty associated with determining the source location of nuclear pollutants in the atmosphere after a nuclear fallout using a numerical model is difficult to determine. Uncertainty can originate from input data (meteorological and emissions), internal model error, physics parameterizations, and stochastic processes. This study uses the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model with data from the 1983 Cross Appalachian Tracer Experiment (CAPTEX) (Ferber et al. 1986) and simulating six nuclear detonations (Rolph et al. 2014) to quantify and communicate uncertainty in ensemble dispersion simulations. This is accomplished by utilizing an ensemble of forward trajectory simulations varying initial conditions ...

Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, 2019 Air Force Institute of Technology

#### Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, David A. Labuda

*Theses and Dissertations*

High-speed Schlieren photography was utilized to visualize flow in the Air Force Research Laboratory Mach 6 Ludwieg tube facility. A 7° half-angle cone/flare model with variable nosetip radius and flare angle options was used in the study. Testing was performed at two driver tube pressures, generating freestream Reynolds numbers of 10.0x10^{6} and 19.8x10^{6} per meter. The variable-angle flare portion of the model provided a method for adjusting the intensity of the adverse pressure gradient at the cone/flare junction. As expected from existing literature, boundary layer separation along the cone frustum occurred further upstream as ...

Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, 2019 Air Force Institute of Technology

#### Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Dustin P. Graves

*Theses and Dissertations*

The analysis of a celestial icosahedron geometry is considered as a potential design for a Vacuum Lighter than Air Vehicle (VLTAV). The goal of the analysis is ultimately to understand the initial fluid-structure interaction of the VLTAV and the surrounding airflow. Up to this point, previous research analyzed the celestial icosahedron VLTAV in relation to withstanding a symmetric sea-level pressure applied to the membrane of the structure. This scenario simulates an internal vacuum being applied in the worst-case atmospheric environmental condition. The next step in analysis is to determine the aerodynamic effects of the geometry. The experimental setup for obtaining ...

Wall Model Large Eddy Simulation Of A Diffusing Serpentine Inlet Duct, 2019 Air Force Institute of Technology

#### Wall Model Large Eddy Simulation Of A Diffusing Serpentine Inlet Duct, Ryan J. Thompson

*Theses and Dissertations*

The modeling focus on serpentine inlet ducts (S-duct), as with any inlet, is to quantify the total pressure recovery and ow distortion after the inlet, which directly impacts the performance of a turbine engine fed by the inlet. Accurate prediction of S-duct ow has yet to be achieved amongst the computational fluid dynamics (CFD) community to improve the reliance on modeling reducing costly testing. While direct numerical simulation of the turbulent ow in an S-duct is too cost prohibitive due to grid scaling with Reynolds number, wall-modeled large eddy simulation (WM-LES) serves as a tractable alternative. US3D, a hypersonic research ...

Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, 2019 Air Force Institute of Technology

#### Tracking Shock Movement On The Surface Of An Oscillating, Straked Semispan Delta Wing, Justin A. Pung

*Theses and Dissertations*

A recent research effort, sponsored by the Air Force Office of Scientific Research, numerically investigated the unsteady aerodynamic flow field around an oscillating, straked, delta wing. The study was centered on determining the importance of the unsteady aerodynamic forces acting as a driver for a nonlinear motion known as limit cycle oscillations. The current effort focused on creating a computational model to compare to the results of previous tests and modeling efforts and discover new information regarding the onset of LCO. The computational model was constructed using the Cartesian overset capabilities of the CREATE-AV™ fixed wing fluid dynamics solver Kestrel ...

Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, 2019 Air Force Institute of Technology

#### Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, Tylor C. Rathsack

*Theses and Dissertations*

The Ultra Compact Combustor (UCC) promises to greatly reduce the size of a gas turbine engine’s combustor by altering the manner in which fuel is burnt. Differing from the common axial flow combustor, the UCC utilizes a rotating flow, coaxial to the engine’s primary axis, in an outboard circumferential cavity as the primary combustion zone. The present study investigates two key UCC facets required to further this combustor design. The first area of investigation is cooling of the Hybrid Guide Vane (HGV). This UCC specific hardware acts as a combustor center body that alters the exit flow angle ...

Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, 2019 Air Force Institute of Technology

#### Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco

*Theses and Dissertations*

Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. The present ...

Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, 2019 Air Force Institute of Technology

#### Analytical Models And Control Design Approaches For A 6 Dof Motion Test Apparatus, Kyra L. Schmidt

*Theses and Dissertations*

Wind tunnels play an indispensable role in the process of aircraft design, providing a test bed to produce valuable, accurate data that can be extrapolated to actual flight conditions. Historically, time-averaged data has made up the bulk of wind tunnel research, but modern flight design necessitates the use of dynamic wind tunnel testing to provide time-accurate data for high frequency motion. This research explores the use of a 6 degree of freedom (DOF) motion test apparatus (MTA) in the form of a robotic arm to allow models inside a subsonic wind tunnel to track prescribed trajectories to obtain time-accurate force ...

Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, 2019 Air Force Institute of Technology

#### Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, Horatio J. Babcock

*Theses and Dissertations*

With the increased demand for lighter, more fuel efficient and smaller gas turbine engines, the impetus to reduce the weight and size of the turbine has become apparent. One approach to reduce this weight is to reduce the number of blades in the turbine. However, to maintain power output, each blade must be capable of supporting a greater amount of lift. While several high-lift turbine profiles have been detailed in literature, most of these profiles have increased endwall losses, despite their desirable mid-span characteristics. To mitigate this endwall loss, a number of active and passive flow approaches have been studied ...

Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, 2019 Air Force Institute of Technology

#### Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, Tara E. Crouch

*Theses and Dissertations*

Direct numerical simulation (DNS) computational fluid dynamic (CFD) calculations were performed on a 30° slice of 7° half-angle cones with increasing nose radii bluntness at Mach 10 while simulating a distributed roughness pattern on the cone surface. These DNS computations were designed to determine if the non-modal transition behavior observed in testing performed at the Arnold Engineering Development Center (AEDC) Hypervelocity Wind Tunnel 9 was induced via distributed surface roughness. When boundary layer transition is dominated by second mode instabilities, an increase in nose radius delays the transition location downstream. However, blunt nose experiments indicated that as the nose radius ...