The mathematical technique of overrelaxation is used here to speed the convergence of a numerical method for solving viscous, incompressible fluid flow problems. The method, called MAC, involves approximating the complete two-dimensional incompressible Navier-Stokes equations with analogous finite-difference equations. The MAC method was developed by the Los Alamos Scientific Laboratory...
Three areas of liquid state theory are considered.
First, Monte Carlo computer simulation of a two-dimensional hard
disk fluid with an imbedded ellipse was undertaken to determine how a
non-spherical molecule affects intermolecular ordering. The
elliptical molecule (with axial ratios of 2, 5 and 10) altered the
isotropic distribution of...
Responses of biological indicators of soil quality to winter cover cropping were measured on soil samples collected from 6 commercial growers' fields and two experiment research stations in the Willamette Valley of Oregon. The research stations were the North Willamette Research and Extension Center (Aurora, OR), and the Oregon State...
More efficient methods are needed for the in-situ evaluation of mass transfer parameters which describe the movement of solutes through aquifer material. The objective of this study was to develop a method for estimating diffusion rate and capacity coefficients using a single-well, "push-pull" tracer test. The method consists of the...
In this work we consider two multiscale applications with tremendous computational complexity at the lower scale. First, we examine a model for charge transport in semicon- ductor structures with heterojunction interfaces. Due to the complex physical phenomena at the interface, the model at the design scale is unable to adequately...
In this work, flow through synthetic arrangements of contacting spheres is studied
as a model problem for porous media and packed bed type flows. Direct numerical
simulations are performed for moderate pore Reynolds numbers in the range,
10 ≤ Re ≤ 600, where non-linear porescale flow features are known to...
Droplet formation from a rigid and a vibration nozzle driven by a pulsing pressure is simulated. Droplet formation is simulated by using one-dimensional model. For the case of droplet formation from a vibration nozzle, the nozzle vibration is simulated by large deflection plate vibration equation. Droplet formation from a rigid...
Jets in crossflow are used in a wide range of engineering applications and have been studied for more than 60 years. The transversal penetration and structure of a jet placed in a crossflow is known to be strongly three-dimensional. It is believed that, by using a pulsed jet inclined in...
Droplet formation from a flexible nozzle plate driven by a prescribed-waveform excitation of a piezoelectric is numerically investigated using a computational fluid dynamics (CFD) model with the VOF method. The droplet generator with a flexible nozzle plate, which is free to vibrate due to the pressure acting on the plate,...
Recent developments in estimation of the survivability of a U.S. Navy transport barge in random seas are extended to improve accuracy. The single Degree-of-Freedom (DOF) model of a extreme roll response of a barge used in previous research is replaced by a 3-DOF roll-heave-sway model to include linear and nonlinear...
Aquifer recharge is generally driven by fluids that move from the Earth’s surface to groundwater through the unsaturated zone, also known as the vadose zone. When the vadose zone is fractured, fluids, which may include contaminants, can move through the fracture network as well as the porous matrix. Such a...
The mathematical and physical connections between three different ways of quantifying linear predictability in geophysical fluid systems are studied in a series of analytical and numerical models. Normal modes, as they are traditionally formulated in the instabilities theories of geophysical fluid dynamics, characterize the asymptotic development of disturbances to stationary...
In this thesis we study a numerical analysis problem motivated by the need to simulate an event such as an oil spill in a deep water environment. Numerical simulation can help to mitigate the disastrous effects of such events by aiding the management of risk assessment and recovery efforts.
However,...
An experiment on solitary wave impact on a vertical cylinder was conducted in the three-dimensional wave basin at the Oregon State University Hinsdale Wave Research Laboratory. The cylinder was designed using mechanic principles and finite element analysis techniques to enable accurate measurement of horizontal force and overturning moment. Video data...
The purpose of this report is to present procedures by which applicants and reviewers can calculate initial dilution and describe the zone of initial dilution surrounding the discharge site. These calculations would be required under regulations proposed by the U.S. Environmental Protection Agency on April 25, 1978 (1) implementing section...
Two-phase flow in helical conduits is important in many industries where reaction between components, heat transfer, and mass transport are utilized as processes. The helical design is chosen for the effects of secondary flow patterns that reduce axial dispersion, increased heat transfer, and also their compact design. The first is...
Random fields are frequently used in computational simulations of real-life processes. In particular, in this work they are used in modeling of flow and transport in porous media. Porous media as they arise in geological formations are intrinsically deterministic but there is significant uncertainty involved in determination of their properties...
Natural stream systems contain a variety of flow geometries which contain flow separation, turbulent shear layers, and recirculation zones. This work focuses on streams with dead zones. Characterized by slower flow and recirculation, dead zones are naturally occurring cutouts in stream banks. These dead zones play an important role in...
This thesis is comprised of two manuscripts based on a laboratory experiment conducted to examine realistic wave forcing on a vertical wall subjected to tsunami loading. The first manuscript examined tsunami force and pressure distributions on a rigid wall that was fronted by a small seawall. Six different seawall heights...
An understanding of natural coastal hazards is essential for improving resilience of coastal communities. Effective management of coastal hazards relies on prediction tools and mitigation structures that have been designed to handle the dynamic coastal system. This dissertation is a collection of manuscripts that cover a diverse range of fundamental...
In this work, a multicomponent lattice Boltzmann model is developed for the simulation of multiphase mixing, reactions, and separations processes. This model is unique in that diffusive mass transfer of a component in the model is driven by gradients of chemical potential. This fundamentally correct description of diffusion accurately captures...
Flow separation is an important phenomenon in fluid dynamics because of the effect it has on lift and drag on immersed bodies. Areas of swirl within a separated flow region may have a distinct effect on the surface forces, modifying the lift and drag characteristics. A correlation between the passage...
Engineering applications often require fast, accurate solutions of fluid flow around freely moving bodies. The massive parallelism enabled by graphics processing unit (GPU) architecture enables high performance, offering a promising alternative to traditional solver acceleration via multicore central processing units (CPU). However, fully harnessing GPU parallelism requires specialized algorithms and...
Centrifugal casting has been a successful
technique for quickly filling molds, but little is
understood about the fluid flow characteristics that occur
during filling. The understanding of these flow
characteristics and the application of this knowledge
should improve the quality of metal parts cast by this
process. The subject of...
There are many options available when selecting a computational model for
two-phase flows. It is important to understand all the features of the model
selected, including when the model is appropriate and how using it may affect
your results. This work examines how volume displacement effects in two-phase
Eulerian-Lagrangian models...
This dissertation introduces a method which
can simulate multi-dimensional Gaussian random
processes by the superposition of sine functions
The fast Fourier transform technique is incorporated into the simulating method to facilitate
saving of computer time.
In view of the fact that the fast Fourier
transform play important roles in digital...
This research involves a numerical study of the
hydrodynamics of gas fluidized beds. We use the continuum
model, treating both gas and particles as
interpenetrating continua. The motion of gas and
particles is strongly coupled by the interactions between
them. For simplicity, we only consider drag forces.
We use MacCormack's...
Fluid-structure interaction (FSI) is a very interesting and challenging multi-disciplinary field involving interaction of a movable or deformable structure with an internal or surrounding fluid flow. FSI has several practical engineering applications such as the determination of the hydrodynamic forces on a structure or the dynamics of motion of bodies...
A numerical model for the simulation of fully-coupled fluid-structure
interaction is developed in this study. In modeling the fluid, the Reynolds
Averaged Navier-Stokes equations are solved for an incompressible viscous
fluid field and a k-ε model is employed for turbulence computations.
Hydrodynamic forces obtained by the integration of the fluid...
A semi-empirical mobility model is presented which predicts tracked vehicle performance in timber harvesting applications. The interactions between the log load and the
terrain, the log load and the vehicle, and the vehicle and the terrain cause resistances for the vehicle. The mobility
model calculates these resistances, comparing them to...
Many engineering devices and propulsion systems suffer from undesirable effects of cavitation; such as degradation in the efficiency of pumps and turbines, generation of noise and vibration on ship propeller, increased drag and erosion of propeller blade, etc.
In spite of decades of research on this problem, detailed study of...
In chapter 3 of our paper we present equations of motion for continuous mass
distribution subject to hydrodynamic forces in their most general form. We start
with equations for discrete mass particles and then transform the equations so
that it is appropriate for a continuous mass distribution. As we do...
Multiphase flow dynamics are important in many naval and turbomachinery applications, where bubble interaction with low pressure, vortical structures can lead to undesirable cavitation effects. To better understand the underlying phenomena, a multiscale numerical framework is developed to simulate bubble laden flow in dynamic hydro propulsion systems. Several subproblems in...
Computer control of a robot arm's motion requires kinematic algorithms for relating the state of a particular arm's joints to the position and orientation of its tool in three-dimensional space. To design such algorithms requires mathematical formulation of the kinematics of the arm. The resulting long, tedious algebraic manipulations suggest...
Understanding the processes involved in the transport of dissolved gas plumes in groundwater aquifers is essential for comprehending the effect that these transport processes can have on site characterization and remedial design applications. Previous laboratory and field studies have indicated that dissolved gas transport in groundwater can be greatly affected...
We discuss a mathematical model arising from the following
physical situation. We consider a gas-filled cylinder with a piston
at one end whose motion is determined by the pressure of the gas
within the cylinder and by external forces. Zero mass flux is
assumed at the piston while the mass...
Micro scale systems are being utilized in a wide variety of chemical, biological and heat exchanger applications, but suffer from the development of vapor bubbles inside the microchannels due to convective boiling, leading to decreases in system performance. In this work, a simulation-based control strategy is employed to eliminate flow...
The United States (US) Department of Energy (DOE) has identified the pebble-bed reactor as a high priority for US research with the end goal of licensing a pebble-bed reactor (PBR) for operation in the United States. Before this can be accomplished significant research must be done regarding the safety of...
The development of a least squares model for the
determination of compliance constants from various combinations
of vibration frequency, mean square amplitudes
of vibration and centrifugal distortion data is discussed.
The resultant model is applied to frequency and mean square
amplitude data for NO₂ and N₂O₄ and to frequency and...
Statistically-based estimation techniques are presented
in this study. These techniques incorporate structural test
data to improve finite element models used for dynamic
analysis.
Methods are developed to identify optimum values of the
parameters of finite element models describing structures.
The parameters which may be identified are : element area,
mass...
This thesis investigates the applicability of the finite element method to model wave energy converter (WEC) hydroelasticity using LS-DYNA. The proposed methodology uses the Arbitrary Lagrangian-Eulerian formulation to model Fluid-Structure Interaction (FSI) between the WEC and the fluid elements. This formulation allows for time-domain modeling of higher order effects such...
To design and precisely control a manipulator requires
developing an efficient dynamic model of the system. The
present work demonstrates how this can be accomplished by
employing Kane's dynamical equations. First, a detailed
manual derivation of the equations of motion for a
particular robot is presented in such way that...
This thesis examines the transient response of a packed bed heat
regenerator when heated from an initial uniform bed temperature. Very large
(1700 K) temperature differences were studied as well as the effect of
simultaneous chemical reaction in the gas phase.
First the effects of temperature on physical and transport...
To facilitate the evaluation and design of structures subjected to fluid loading, a study of fluid-structure interaction (FSI) using the particle finite element method (PFEM) is presented to approximate the responses and sensitivities of structures which interact with fluid. A wide range of structural types are permissible by making no...
Uptake, in-plant transport, and local accumulation of organic
chemicals by plants are influenced by plant characteristics, properties
of the chemical and the soil, and by environmental conditions. Evaluations
of plant contamination required by regulatory agencies cannot be
made experimentally for the many thousands of xenobiotic chemicals in
existence or being...
A brushless doubly-fed machine (BDFM) is a single-frame, self-cascaded
induction machine capable of operating in both the induction
and the synchronous modes. This thesis presents some important
advances concerning dynamic modeling, simulation and analysis of the
BDFM.
Initially, a two-axis model and its associated parameters are developed
and calculated. The...
The algorithm RLS-PLUS was developed to yield solutions to the
multivariate control problem of diameter and species optimization for mixed conifer
and hardwood stands. The problem is specified with twenty-five state variables
consisting of five species groups with four merchantable diameter classes and one
unmerchantable class. This gives twenty diameter...
In this dissertation, a group of vehicle dynamics simulation tools is developed with two primary goals: to accurately represent vehicle behavior and to provide insight that improves the understanding of vehicle performance. Three tools are developed that focus on tire modeling, vehicle modeling and lap time simulation.
Tire modeling is...
Equations for predicting the probability of a tree's dying in the
next 5 years are presented for eight conifer and eight hardwood
tree species from southwest Oregon. A logistic equation form was
used to characterize the probability of mortality. The parameters
of the equation were estimated using weighted, maximum likelihood...
A numerical model, simulating the complex behavior of reinforced soil walls using the finite element method, was developed to evaluate the behavior of a surcharged, geosynthetic-reinforced retaining wall with modular block facing. A nonlinear elastic-plastic constitutive soil material model was calibrated to experimental plane strain test data, while the performance...
CTSPAC is a mathematical model for coupled transport of water, solutes, and thermal
energy in the soil-plant-atmosphere continuum. The mathematical structure consists
of coupling a model for transport through soil (soil submodel) to one for xylem and phloem
transport (plant submodel). The modeling approach is based on discrete space conceptualization...
Recent tsunami field surveys from the 2011 Great East Japan Earthquake and Tsunami have recorded numerous examples of tsunami-induced soil instability: significant scour around foundations, foundation failure of piles, and other damage caused by liquefaction. From the observations of soil instability leading to the failure of critical coastal structures, it...
The low-level baroclinic eddy activity seen in the NASA Ames Mars General Circulation Model (MGCM) for simulations under three annual dust cycles are characterized. Simulations were conducted with both radiatively active and radiatively inert clouds (RAC and non-RAC, respectively) for 11 continuous annual cycles for each dust case. Model results...
The vegetation in Yosemite National Park changed during the 20th century and may change in the 21st century in response to climate change. Vegetation surveys made during the 1930s and the 1990s provide benchmark records separated by 60 years. This study uses the MC1 dynamic global vegetation model to forecast...
Wave energy holds great promise to be part of the alternative energy portfolio that will provide independence from fossil fuels. As wave energy converter (WEC) technologies mature, designing effective control strategies to extract maximum energy, extend device life, coordinate WEC operation within an array, or mitigate negative impacts of a...
This thesis contains three parts addressing the asymptotic analysis of fluid flow through fully saturated porous medium in the presence of an adjacent thin channel.
In the first part the problem is modeled by Darcy's law in both the porous medium and in the channel. The permeability in the channel...