| Generating Delft3D Boundary Conditions Using the Navy Coastal Ocean Model |
20 Dec 2012 |
16 pages |
| Authors:
Kacey Edwards; Tiffany Nguyen; David Sitton; NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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 | The Delft3D modeling system is often used to provide operational forecasts of littoral hydrodynamics. One method of providing boundary conditions to the system is to extract data from regional model results. Software was developed to extract data from results of the Navy Coastal Ocean Model (NCOM) and to write DElft3D-FLOW boundary conditions. The software was used to generate boundary conditions for a variety of Delft3D-FLOW scenarios, and the generated boundary ... |
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| Functional Entropy Variables: A New Methodology for Deriving Thermodynamically Consistent Algorithms for Complex Fluids, with Particular Reference to the Isothermal Navier-Stokes-Korteweg Equations |
Nov 2012 |
63 pages |
| Authors:
Ju Liu; Hector Gomez; John A Evans; Thomas J Hughes; Chad M Landis; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| We propose a new methodology for the numerical solution of the isothermal Navier-Stokes- Korteweg equations. Our methodology is based on a semi-discrete Galerkin method invoking functional entropy variables, a generalization of classical entropy variables, and a new time integration scheme. We show that the resulting fully discrete scheme is unconditionally stable-in-energy, second-order time-accurate, and mass-conservative. We utilize isogeometric analysis for spatial discretization and verify the aforementioned properties by adopting the ... |
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| Genetic Algorithm Optimization of a Film Cooling Array on a Modern Turbine Inlet Vane |
Sep 2012 |
374 pages |
| Authors:
Jamie J Johnson; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| In response to the need for more advanced gas turbine cooling design methods that factor in the 3-D flowfield and heat transfer characteristics, this study involves the computational optimization of a pressure side film cooling array on a modern turbine inlet vane. Latin hypersquare sampling, genetic algorithm reproduction, and Reynolds-Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) as an evaluation step are used to assess a total of 1,800 film ... |
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| Geometric Methods for Infinite-Dimensional Dynamical Systems |
27 Aug 2012 |
8 pages |
| Authors:
Bjorn Sandstede; BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS
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| This was a conference grant for the conference 'Geometric Methods for Infinite-Dimensional Dynamical Systems' held November 4-6, 2011 at Brown University. The plenary and topical talks formed the heart of the conference. They featured the four mathematical themes of the conference: data assimilation, geometric singular perturbation theory, nonlinear optics and traveling waves. |
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| Development of High-Order Method for Multi-Physics Problems Governed by Hyperbolic Equations |
01 Aug 2012 |
41 pages |
| Authors:
John A Ekaterinarius; FOUNDATION FOR RESEARCH AND TECHNOLOGY-HELLAS HERAKLION CRETE (GREECE)
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| In this section we present the discontinuous Galerkin (DG) discretization of the three dimensional Euler and Nervier-Stokes equations for hybrid-type meshes. Without loss of generality the general finite element discretization framework is presented for hexahedral type meshes since all computations of the DG method are performed at the computational domain on the standard cubic element and transferred back to the physical domain elements (tetrahedras, prisms, pyramids, or hexahedras) using collapsed ... |
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| Discrete Spectrum Analyses for Various Mixed Discretizations of the Stokes Eigenproblem |
Aug 2012 |
11 pages |
| Authors:
John A Evans; Thomas J Hughes; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| We conduct discrete spectrum analyses for a selection of mixed discretization schemes for the Stokes eigenproblem. In particular, we consider the MINI element, the Crouzeix-Raviart element, the Marker-and- Cell scheme, the Taylor-Hood element, the Q(sub k)/P(sub k-1) element, the divergence-conforming discontinuous Galerkin method, and divergence-conforming B-splines. For each of these schemes, we compare the spectrum for the continuous Stokes problem with the spectrum for the discrete Stokes problem, and we ... |
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| Three-Dimensional Flow Modeling of McNary Dam Forebay, Columbia River |
Aug 2012 |
55 pages |
| Authors:
E A Hammack; David S Smith; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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| The U.S. Army Corps of Engineers, Walla Walla District (NWW), requested that the U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory (ERDC-CHL) model the flow conditions of McNary Dam forebay. The different flows are produced by various powerhouse/spillbay operating conditions for certain river discharges. The flow conditions, powerhouse operation schedule, and spillbay opening geometry were provided by NWW. This report contains a description of the geometry, meshing, ... |
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| High-Order Space-time Discontinuous Galerkin Cell Vertex Scheme toward Compressible Navier Stokes Equations |
25 Jun 2012 |
40 pages |
| Authors:
Shuangzhang Tu; JACKSON STATE UNIV MS
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| This project continues our previous AFOSR project (Grant No. FA9550-08-1-0122) to extend and verify our high order space-time cell vertex scheme (DG-CVS) toward solving the compressible Navier-Stokes equation. The DG-CVS method integrates the best features of the space-time Conservation Element/Solution Element (CE/SE) method [1] and the discontinuous Galerkin (DG) method [2]. The core idea is to construct a staggered space-time mesh through alternate cell-centered CEs and vertex-centered CEs (cf. Fig. ... |
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| Transition and Transport in Turbomachinery |
Jun 2012 |
11 pages |
| Authors:
Paul A Durbin; IOWA STATE UNIV AMES DEPT OF AEROSPACE ENGINEERING
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| The interaction of discrete and continuous Orr-Sommerfeld modes in a boundary layer is studied by computer simulation. The discrete mode is an unstable Tollmein-Schlichting wave. The continuous modes generate jet-like disturbances inside the boundary layer. Either mode alone does not cause transition to turbulence; however, the interaction between them does. The continuous mode jets distort the discrete modes, producing Lambda shaped vortices. Breakdown to turbulence is subsequent. The lateral spacing ... |
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| Physics-Based Design of Micro Air Vehicles |
Apr 2012 |
53 pages |
| Authors:
Richard D Snyder; Philip Beran; Raymond Kolonay; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIRECTORATE
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| Micro air vehicles, especially those that use flapping wings for propulsion and control, are characterized by complex, time-dependent, nonlinear interactions amongst a variety of physical disciplines. These interactions must be carefully controlled to attain desired levels of performance, but the number and range of parameters that describe possible micro aircraft is extremely large, poorly explored, and inadequately understood. Aerodynamic, structural, kinematic, and mechanical parameters are relevant and may be strongly ... |
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| Isogeometric Divergence-conforming B-splines for the Steady Navier-Stokes Equations |
Apr 2012 |
72 pages |
| Authors:
John A Evans; Thomas J Hughes; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| We develop divergence-conforming B-spline discretizations for the numerical solution of the steady Navier-Stokes equations. These discretizations are motivated by the recent theory of isogeometric discrete differential forms and may be interpreted as smooth generalizations of Raviart-Thomas elements. They are (at least) patchwise C0 and can be directly utilized in the Galerkin solution of steady Navier-Stokes flow for single-patch configurations. When applied to incompressible flows, these discretizations produce pointwise divergence-free velocity ... |
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| Isogeometric Divergence-conforming B-splines for the Unsteady Navier-Stokes Equations |
Apr 2012 |
49 pages |
| Authors:
John A Evans; Thomas J Hughes; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| Divergence-conforming B-splines are developed for application to the incompressible Navier-Stokes equations on geometrically mapped domains. These enable smooth pointwise divergence-free solutions and thus satisfy mass conservation in the strongest possible sense. Semi-discrete methods based on divergence-conforming B-splines are shown to conserve linear and angular momentum and satisfy balance laws for energy vorticity, enstrophy, and helicity. These are geometric structure-preserving quantities and numerical simulations that are sensitive to them are shown ... |
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| Continuous and Discontinuous Galerkin Methods for a Scalable Three-Dimensional Nonhydrostatic Atmospheric Model: Limited-Area Mode |
09 Mar 2012 |
44 pages |
| Authors:
James F Kelly; Francis X Giraldo; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF APPLIED MATHEMATICS
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| This paper describes a unified, element based Galerkin (EBG) framework for a three-dimensional, nonhydrostatic model for the atmosphere. In general EBG methods possess high-order accuracy, geometrical flexibility, excellent dispersion properties and good scalability. Our nonhydrostatic model, based on the compressible Euler equations, is appropriate for both limited-area and global atmospheric simulations. Both a Continuous Galerkin (CG), or spectral element, and discontinuous Galerkin (DG) model are considered using hexahedral elements. The ... |
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| Accurate Modeling of Stability and Control Properties for Fighter Aircraft from CFD |
Mar 2012 |
196 pages |
| Authors:
Jedediah H Butler; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| Difficulties in obtaining accurate Stability and Control (S&C) data for nonlinear regions in the flight envelope early in the design phase often lead to costly fixes late in the acquisition process. Work examined herein addresses this problem by utilizing recent advances in Computational Fluid Dynamics (CFD) to create a high-fidelity database before any parts have to be physically produced. In combination with CFD, System Identification (SID) is used to characterize ... |
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| High Order Strong Stability Preserving Time Discretizations for the Time Evolution of Hyperbolic Partial Differential Equations |
01 Feb 2012 |
9 pages |
| Authors:
Sigal Gottlieb; MASSACHUSETTS UNIV DARTMOUTH DEPT OF MATHEMATICS
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| The objective of this project is to develop and analyze stable time discretizations suitable for the simulation of hyperbolic time-dependent partial differential equations. Implicit and explicit multi-step multi-stage time discretizations with optimal time-step restrictions have been developed, as well as implicit Runge--Kutta methods with downwinding and unconditional stability. A testing suite has been written to test some of these methods with a variety of spatial discretizations. New directions have been ... |
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| Using RANS Calculations of Turbulent Kinetic Energy to Provide Two Point Flow Velocity Correlations and Surface Pressure Spectra |
31 Jan 2012 |
58 pages |
| Authors:
Stewart A Glegg; FLORIDA ATLANTIC UNIV BOCA RATON
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| This report gives the results of a study that used the linearized Navier Stokes equations to model spectra in turbulent flows. The first part of the study considers two dimensional wakes and provides estimates of two point correlation functions and spectra from the distribution of turbulent kinetic energy in the flow. In the second part of the study a turbulent boundary layer in the vicinity of a forward facing step ... |
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| Pulsed Plasma Arrays for Tubulence Control |
31 Jan 2012 |
16 pages |
| Authors:
Haris J Catrakis; CALIFORNIA UNIV IRVINE
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| The PI successfully achieved active control of flow separation using dielectric barrier discharge plasma actuation on a hemisphere mounted on an elevated flat surface in a wind tunnel. Visualization of streaklines in the flow around the hemisphere at Re = 40,000 for control-on vs. control-off showed a reduction in the size of the separation region with active flow control. Measurement of the surface pressure coefficient also showed a recovery in ... |
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| Efficient FMM Accelerated Vortex Methods in Three Dimensions via the Lamb-Helmholtz Decomposition |
25 Jan 2012 |
20 pages |
| Authors:
Nail A Gumerov; Ramani Duraiswami; MARYLAND UNIV COLLEGE PARK INST FOR ADVANCED COMPUTER STUDIES
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| Vortex-element methods are often used to efficiently simulate incompressible flows using Lagrangian techniques. Use of the FMM (Fast Multipole Method) allows considerable speed up of both velocity evaluation and vorticity evolution terms in these methods. Both equations require field evaluation of constrained (divergence free) vector valued quantities (velocity, vorticity) and cross terms from these. These are usually evaluated by performing several FMM accelerated sums of scalar harmonic functions. We present ... |
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| Average Power and Brightness Scaling of Diamond Raman Lasers |
07 Jan 2012 |
33 pages |
| Authors:
Richard Mildren; MACQUARIE UNIV SYDNEY (AUSTRALIA) DEPT OF PHYSICS
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| Diamond holds substantial promise as a high Raman gain laser material with outstanding power handling capability, yet despite this the highest reported output power from a diamond Raman laser prior to this project was approximately 1 W. This report describes investigations into order-of-magnitude power scaling of diamond Raman lasers. The investigations focus on 1064 nm beam conversion of 50 W lasers in the external cavity Raman cavity configuration in both ... |
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| On the Propagation of Nonlinear Acoustic Waves in Viscous and Thermoviscous Fluids |
Jan 2012 |
9 pages |
| Authors:
P M Jordan; G V Norton; S A Chin-Bing; A Warn-Varnas; NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS
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| Acoustic travelling waves are studied in the context of nonlinear propagation in Newtonian fluids. First we examine the one-dimensional (1D) versions of four weakly-nonlinear acoustic models, all of which admit known travelling wave solutions (TWS)s in the form of Taylor shocks. Next, we derive the exact but implicit, kink-type TWS of the compressible 1D Navier-Stokes equations under the homentropic assumption. Then, using three simple metrics, we numerically compare the TWSs ... |
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| Aerodynamic Analysis of the M33 Projectile Using the CFX Code |
Dec 2011 |
97 pages |
| Authors:
Chee H Wong; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| The M33 projectile has been analyzed using the ANSYS CFX code that is based on the numerical solution of the full Navier-Stokes equations. Simulation data were obtained against various Mach numbers ranging from M= 0.5 to M2.6 at 0 and 2 angles of attack. Simulation data were also obtained against various angles of attack from 0 to 85 for M= 0.5. For Mach numbers between M= 0.5 to 2.6, the ... |
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| Numerical Schemes for Dynamically Orthogonal Equations of Stochastic Fluid and Ocean Flows |
03 Nov 2011 |
62 pages |
| Authors:
M P Ueckermann; P F Lermusiaux; T P Sapsis; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
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| The quantification of uncertainties is critical when systems are nonlinear and have uncertain terms in their governing equations or are constrained by limited knowledge of initial and boundary conditions. Such situations are common in multiscale, intermittent and non-homogeneous fluid and ocean flows. The Dynamically Orthogonal (DO) field equations provide an efficient time-dependent adaptive methodology to predict the probability density functions of such flows. The present work derives efficient computational schemes ... |
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| Trajectory Prediction of Spin-Stabilized Projectiles With a Steady Liquid Payload |
Nov 2011 |
30 pages |
| Authors:
Gene R Cooper; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| Payloads that behave like a liquid are carried on board some projectile configurations, and it is well established that the internal motion of a liquid payload can induce destabilizing moments on the projectile. This report creates a method to include the effect of a liquid payload in the flight dynamic equations of motion, enabling trajectory simulations of projectiles with liquid payloads. To include this effect, liquid payload moments are added ... |
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| Towards a Fast Dynamic Model of the Human Circulatory System |
06 Oct 2011 |
35 pages |
| Authors:
M A Green; C R Kaplan; J P Boris; E S Oran; NAVAL RESEARCH LAB WASHINGTON DC
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| We describe a model for blood transport in the human circulatory system that is based on a set of equations for an unsteady elastic pipe-flow circuit. The Navier-Stokes equations are collapsed from three spatial dimensions and time to one spatial dimension and time by assuming axisymmetric vessel geometry and a parabolic velocity profile across the cylindrical vessels. Contractions of a beating heart that drive the fluid are modeled as prescribed ... |
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| Theory and Modeling of Internal Wave Generation in Straits |
30 Sep 2011 |
8 pages |
| Authors:
Karl R Helfrich; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY
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| The long-term goal of this research is to improve scientists' understanding of the generation of nonlinear internal tides and waves by stratified flow over sills (e.g,. straits) and shelves and the subsequent evolution of the radiated internal disturbance, with particular emphasis on the role of rotation. The primary objectives will be to connect the generation process with the dynamics of the disintegration of the radiated internal tide into shorter, nonlinear ... |
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| Near-Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves |
30 Sep 2011 |
9 pages |
| Authors:
Peter J Diamessis; Gustaaf B Jacobs; CORNELL UNIV ITHACA NY SCHOOL OF CIVIL ENGINEERING
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| The long-term goal of this work is to develop a fundamental understanding of the underlying physics of the interaction of nonlinear internal waves (NLIWs) with the continental shelf seafloor over a broad range of environmental conditions. We are particularly interested in how such interactions impact underwater optics and acoustics and shelf energetics and ecology by simulating enhanced bottom boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ... |
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| Impact of Typhoons on the Western Pacific Ocean DRI: Numerical Modeling of Ocean Mixed Layer Turbulence and Entrainment at High Winds |
30 Sep 2011 |
6 pages |
| Authors:
Ramsey R Harcourt; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
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| This ongoing collaborative effort aims at measuring and modeling the response of the upper ocean to strong typhoons both in simple, open ocean conditions and in the more complex conditions caused by ocean eddies and preconditioning by prior storms. The measurement and modeling activities include a focus on the impact of surface waves; air-sea fluxes; and the temperature, salinity, and velocity structure of the upper ocean. The goals of this ... |
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| Interactions of Waves and River Plume and their Effects on Sediment Transport at River Mouth |
30 Sep 2011 |
9 pages |
| Authors:
Tian-Jian Hsu; Fengyan Shi; DELAWARE UNIV NEWARK CENTER FOR APPLIED COASTAL RESEARCH
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| To develop a robust coastal/nearshore modeling system for river plume dynamics, sediment deposition/resuspension and inlet morphodynamics in a wave-dominated, high sediment yield and highly stratified environment. To develop a detailed wave-resolving Reynolds-Averaged Navier-Stokes model for wave-current sediment interactions in well-mixed and salt-stratified conditions. To study the interactions between tidal flow, waves and riverine outflow and their effects on sediment transport and morphodynamics using NearCOM and FVCOM. To develop parameterizations of ... |
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| On Convergence of the Immersed Boundary Method for Elliptic Interface Problems |
29 Sep 2011 |
13 pages |
| Authors:
Zhilin Li; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| Peskin's Immersed Boundary (IB) method is one of the most popular numerical methods for many years and has been applied to problems in mathematical biology, fluid mechanics material sciences, and many other areas. Peskin's IB method is associated with discrete delta functions. It is believed that the IB method is first order accurate in the L(infinity) norm. But almost none rigorous proof could be found in the literature until recently ... |
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| Using a Volume Bragg Grating Instead of a Faraday Isolator in Lasers Incorporating Stimulated Brillouin Scattering Wavefront Reversal or Beam Cleanup |
29 Aug 2011 |
6 pages |
| Authors:
John E McElhenny; Jeffrey O White; Steven D Rogers; Tigran Sanamyan; Leonid B Glebov; Oleksiy Mokhun; Vadim I Smirnov; ARMY RESEARCH LAB ADELPHI MD
|
| A master-oscillator power-amplifier with stimulated Brillouin scattering (SBS) beam cleanup or wavefront reversal typically incorporates a Faraday isolator to outcouple the Stokes light, limiting the power scalability. Volume Bragg gratings (VBGs) have the potential for scaling to higher powers. We report here the results of tests on a VBG designed to resolve wavelengths 0.060 nm apart, corresponding to the 16 GHz frequency shift for SBS backscattering at 1064 nm in ... |
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| Numerical Schemes and Computational Studies for Dynamically Orthogonal Equations (Multidisciplinary Simulation, Estimation, and Assimilation Systems: Reports in Ocean Science and Engineering) |
Aug 2011 |
49 pages |
| Authors:
Mattheus P Ueckermann; Pierre F Lermusiaux; Themis P Sapsis; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
|
| The quantification of uncertainties is critical when systems are nonlinear and have uncertain terms in their governing equations or are constrained by limited knowledge of initial and boundary conditions. Such situations are common in multiscale, intermittent and non-homogeneous fluid and ocean flows. The Dynamically Orthogonal (DO) field equations provide an efficient time-dependent adaptive methodology to predict the probability density functions of such dynamics. This work derives efficient computational schemes for ... |
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| Development of the Nonhydrostatic Unified Model of the Atmosphere (NUMA): Limited-Area Mode (Preprint) |
14 APR 2011 |
36 pages |
| Authors:
James F. Kelly; Francis X. Giraldo; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF APPLIED MATHEMATICS
|
| This paper describes a Nonhydrostatic Unified Model of the Atmosphere (NUMA) based on a spectral element, or high-order continuous Galerkin (CG) spatial discretization utilizing 3D hexahedral elements. The nonhydrostatic dynamical core, based on the compressible Euler equations, is appropriate for both limited-area and global atmospheric simulations. In this paper we restrict our attention to 3D limited-area phenomena; global atmospheric simulations will be presented in a follow-up paper. A suite of ... |
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| Computational Electromagnetics |
20 Feb 2011 |
9 pages |
| Authors:
Oscar P Bruno; CALIFORNIA INST OF TECH PASADENA
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| The overall work in the proposed areas for the duration of this effort, through November 2010, is detailed in what follows. In particular, our efforts gave rise to 1) Volumetric propagation and scattering solvers for propagation through thousand of kilometers of realistic three-dimensional atmospheres (completed in 2009); 2) Development of high-order solvers, which do not suffer from restrictive CFL conditions, for solution of time-dependent wave-propagation problems in inhomogeneous media; 3) ... |
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| Ground Test and Computation of Boundary Layer Transition on the Hypersonic International Flight Research and Experimentation (HIFiRE)-5 Vehicle |
Feb 2011 |
93 pages |
| Authors:
Roger Kimmel; David Adamczak; Ryan Gosse; Karen Berger; Shann Rufer; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIRECTORATE
|
| The HIFiRE Flight 5 payload was assessed in the NASA LaRC 20-Inch Mach 6 Air Tunnel. The primary objectives were to determine the boundary layer transition characteristics and the effectiveness trips. Boundary layer profiles were extracted from Navier-Stokes calculations of the flow field, and were used to assess trip heights in terms of typical trip correlating parameters. Leading-edge roughness was well-correlated with the R-bar-star parameter. This correlation was used to ... |
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| Simulating the Detachment of Leading Edge Vortices on Drosophila Melanogaster Using CFD |
13 Sep 2010 |
7 pages |
| Authors:
Alex Sabbatini; Gabriel Smith; Jeffrey S Pulskamp; Ronald G Polcawich; STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING
|
| Initial CFD simulations of quasi-steady hovering flight of the Drosophila sp. have studied the effects of delayed rotation of the wings at the end of each stroke and it s effect on the resulting unsteady aerodynamic forces found throughout the wing [8]. Further studies were carried out using the same CFD model as before to determine the lift and power requirements for Drosophila Virilis [7]. To verify the validity of ... |
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| Investigation of Cavity Flow Effects on Store Separation Trajectories |
07 May 2010 |
84 pages |
| Authors:
Luke P Finney; NAVAL ACADEMY ANNAPOLIS MD
|
| In this study, a cavity previously used as part of the Navy Internal Carriage and Separation (NICS) experiments will be used in conjunction with the Mark 82 (500 lb class) store to compare previously obtained wind tunnel data to CFD results for an internal bay/store configuration. Forces and moments for the store along the horizontal traverse will be found using a specific single equation turbulence model (Spalart-Allmaras) in order to ... |
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| Optical Model Reduction and Robust Feedback Control for Aerodynamics |
29 MAR 2010 |
56 pages |
| Authors:
Seddik M. Djouadi; TENNESSEE UNIV KNOXVILLE
|
| In this project, methods of model reduction that integrate feedback active flow control with applications to nonlinear convection and turbulent flows governed by Navier-Stokes equations are developed. A new methodology which extracts boundary conditions in reduced order proper orthogonal decomposition (POD) and finite difference models is developed. A new model reduction method based on empirical data and balanced truncation was developed and applied to nonlinear Galerkin models. Based on this ... |
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| Numerical Simulation of Propeller Performance with an Inclined Shaft Arrangement |
MAR 2010 |
40 pages |
| Authors:
Seth Schroeder; Charles Dai; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD RESISTANCE AND PROPULSION DIV
|
| A propeller in an inclined shaft arrangement has been simulated using a Reynolds-Averaged Navier-Stokes solver. The commercially available codes Ansys' Fluent and IcemCFD were used for the numerical simulation. The method has been demonstrated through a series of simulations advancing in complexity. The simulations begin with steady-state, single blade calculations and advance to fully unsteady, full 360 deg domain calculations. Each simulation is supported through comparison with experimental data. This ... |
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| Hybrid LES/RANS Simulation of the Effects of Boundary Layer Control Devices Using Immersed Boundary Methods |
22 FEB 2010 |
76 pages |
| Authors:
Jack R. Edwards; NORTH CAROLINA STATE UNIV AT RALEIGH
|
| This work has developed an extension of an existing immersed-boundary (IB) method to compressible, turbulent flows and has investigated its use in simulating the effects of different types of flow control devices: micro vortex generators, bleed-hole arrays, aeroelastically-deforming "mesoflaps", and boundary layer trips. The IB method has been used with Reynolds-averaged Navier-Stokes (Menter SST) and hybrid large-eddy simulation / Reynolds averaged Navier-Stokes (LES/RANS) turbulence closures. The method has been applied ... |
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| Studies of the Electrohydrodynamic Force Produced in a Dielectric Barrier Discharge for Flow Control. Report no. 2, Phase 3 |
FEB 2010 |
52 pages |
| Authors:
Jean-Pierre Boeuf; T. Unfer; L. Pitchford; UNIVERSITE PAUL SABATIER TOULOUSE (FRANCE)
|
| The mechanisms of ion wind generation in surface dielectric barrier discharges (SDBDs) is identical to the one in corona discharges. The electrohydrodynamic force (EHD) generated in SDBDs for moderate increase rates of the applied voltage is, as in corona discharges, due to the development of a unipolar region above the dielectric surface, where ion space charge is dominant and ions transfer momentum to the neutral gas. For very fast rise ... |
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| High-Fidelity Simulations of Moving and Flexible Airfoils at Low Reynolds Numbers (Postprint) |
Feb 2010 |
22 pages |
| Authors:
Miguel R Visbal; Raymond E Gordnier; Marshall C Galbraith; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIR/ AERONAUTICAL SCIENCES DIV/COMPUTATIONAL SCIENCES BRANCH
|
| The present paper highlights results derived from the application of a high-fidelity simulation technique to the analysis of low-Reynolds-number transitional flows over moving and flexible canonical configurations motivated by small natural and man-made flyers. This effort addresses three separate fluid dynamic phenomena relevant to small fliers, including: laminar separation and transition over a stationary airfoil, transition effects on the dynamic stall vortex generated by a plunging airfoil, and the effect ... |
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| Calculating Forces on Components of Hydraulic Structures |
Aug-2009 |
12 pages |
| Authors:
E A Hammack; Moira T Fong; Richard L Stockstill; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
|
| This Coastal and Hydraulics Engineering Technical Note (CHETN) demonstrates a means of calculating hydraulic forces acting on submerged surfaces of hydraulic structures. The primary concern in evaluating the hydraulic performance of a structure is whether it can withstand the imposed hydraulic forces. Forces acting on components such as stilling basins, spillway faces, bridge piers, culvert valves, spillway gates, lock guard walls, floodwalls, etc., must be accurately estimated to ensure appropriate ... |
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| Thrust Augmentation in Solid Rocket Motors Using Beamed Microwave Energy |
13-Jul-2009 |
13 pages |
| Authors:
Natalia E Gimelshein; Sergey F Gimelshein; Andrew Ketsdever; ENGINEERING RESEARCH AND CONSULTING INC (ERC INC) EDWARDS AFB CA
|
| Feasibility of using beamed microwave energy to increase thrust of solid rocket motors during launch is analyzed. Coupling of microwave radiation with internal energies of micron-sized alumina particles and the successive transfer of internal energy of particles to thermal and then kinetic energy of gas is expected to be the main mechanism of thrust increase. A two-phase two-way coupled capability has been developed. For the gas phase, the capability applies ... |
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| Influence of Structural Flexibility on Flapping Wing Propulsion |
Jun-2009 |
180 pages |
| Authors:
Aaron M McClung; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The influence of structural deformations on the aerodynamic response of a flapping wing configuration was examined using Navier-Stokes based simulation. Two deformation modes, torsion and bending, were considered for an elastic axis along the leading edge of the wing. Both deformation modes influence the velocity and acceleration profile of the wing surface, altering the unsteady aerodynamic phenomena produced by the dynamic wing motion. The spanwise feathering rotation, or torsional response, ... |
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| Implicit and P-Multi-Grid Algorithms for High-Order Spectral Difference Method on Unstructured Grids |
May-2009 |
6 pages |
| Authors:
Z J Wang; IOWA STATE UNIV AMES DEPT OF AEROSPACE ENGINEERING
|
| The development of high-order methods (order of accuracy 2nd order) on unstructured grids is widely viewed as a major pacing item in computational fluid dynamics (CFD). Efficient high-order methods capable of handling complex geometries are required to compute vortex dominated flows, and to perform large eddy simulation and direct numerical simulation with complex configurations, and to predict aeroacoustic noise generation and propagation. The primary objective of the present research is ... |
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| Interface Conditions for Hybrid RANS/LES Simulations of Complex and Compressible Flows |
06-Mar-2009 |
31 pages |
| Authors:
Ugo Piomelli; Elias Balaras; MARYLAND UNIV COLLEGE PARK DEPT OF MECHANICAL ENGINEERING
|
| We have demonstrated the applicability of synthetic turbulence coupled with the controlled-forcing method to generate eddies at the interface between RANS and LES in hybrid calculations. We obtained shorter transition regions and improved model accuracy. Realistic turbulence can be generated within 5 boundary-layer thicknesses of the RANS/LES interface even in cases in which the data supplied by the RANS is inaccurate, or the assumptions on which the forcing is based ... |
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| An Investigation of Shock Wave Physics via Hybrid CFD-BGK Solution Methods for Nonequilibrium Flows |
Mar-2009 |
92 pages |
| Authors:
Brook I Bentley; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The Unified Flow Solver, a hybrid continuum-rarefied code, is used to investigate the internal structure of a normal shock wave for a Mach range of 1.55 to 9.0 for Argon, and 1.53 to 3.8 for diatomic Nitrogen. Reciprocal shock thickness, density, temperature, heat flux, and the velocity distribution function are calculated for a one-dimensional shock wave and compared with experimental data from Alsmeyer and DSMC results from Bird. Using the ... |
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| Hybrid LES of Detonations in Reacting Multi-Phase Mixtures |
28-Feb-2009 |
166 pages |
| Authors:
Suresh Menon; Franklin Genin; GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING
|
| A Large-Eddy Simulation (LES) methodology adapted to the resolution of high Reynolds number turbulent flows in supersonic conditions was proposed and developed. A novel numerical scheme was designed, that switches from a low-dissipation central scheme for turbulence resolution to a flux difference splitting scheme in regions of discontinuities. A state-of-the-art closure model was extended in order to take compressibility effects and the action of shock / turbulence interaction into account. ... |
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| An Optimization Framework Based on Domain Decomposition and Model Reduction |
27-Feb-2009 |
21 pages |
| Authors:
Matthias Heinkenschloss; Danny C Sorensen; RICE UNIV HOUSTON TX DEPT OF COMPUTATIONAL AND APPLIED MATHEMATICS
|
| This collaborative research has developed rigorous mathematical and computational frameworks for reduced order model (ROM) generation and the use of ROMs in real-time, design, control, and probabilistic applications of relevance to the Air Force. This research has provided theoretical analyses and numerical studies for several new/extensions of existing ROM approaches, such as goal-oriented, model-constrained approach, balanced truncation model reduction (BTMR) of descriptor systems, and the integration of domain decomposition and ... |
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| Integrated Computational/Experimental Study of Turbulence Modification and Mixing Enhancement in Swirling Jets |
07-Jan-2009 |
30 pages |
| Authors:
J Naughton; D Stanescu; S Heinz; R Semaan; M Stoellinger; C Zemtsop; WYOMING UNIV LARAMIE
|
| Swirling jet flows have been studied experimentally and computationally and the results have been compared with theory. Three-component Laser Doppler Anemometry (LDA) measurements have been carried out for swirling jets of various strengths and swirl distributions. Radial profiles of velocity have been obtained from the jet exit to 50 diameters downstream. The experimental results are consistent with previous results and with similarity theory for weakly swirling turbulent jets. However, the ... |
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