A possible means of submersible detection is through the presence of surface signatures generated by a submerged body propagating in a stratified fluid. Direct numerical simulations (DNS) of perturbations generated by a submerged body can provide insight into how and when surface signatures occur based upon environmental conditions realized in the world's oceans. The use of realistic background stratifications is key to determining the significance of the phenomena to Navy operations and future...

Topics: IDENTIFIERS SURFACE SIGNATURE, DIRECT NUMERICAL SIMULATION, DIMENSIONAL ANALYSIS

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249

May 27, 2011
05/11

by
Prestwich, Andre

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The ROSAT High Resolution Imager has a limited (2-band) spectral response. This spectral capability can give X-ray hardness ratios on spatial scales of 5 arcseconds. The spectral response of the center of the detector was calibrated before the launch of ROSAT, but the gain decreases-with time and also is a function of position on the detector. To complicate matters further, the satellite is ''wobbled'', possibly moving a source across several spatial gain states. These difficulties have...

Topics: ISOTROPIC TURBULENCE, DIRECT NUMERICAL SIMULATION, KOLMOGOROV THEORY, ENERGY SPECTRA, REYNOLDS...

In the present study, we identify the need for high accuracy computing for capturing the transition to turbulence for the flow past a natural laminar flow aerofoil by direct numerical simulation. The major computational elements which contribute error in performing DNS have been identified here and systematically shown to be removed by appropriate grid, numerical method and post-processing tools. We have shown a better way of generating orthogonal grid around thick and cambered aerofoil which...

Topics: Direct Numerical Simulation, Bypass Transition, NLF Aerofoil, Orthogonal Grid, Multi-dimensional...

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274

Jun 2, 2011
06/11

by
Choi, Sung R.; Gyekenyesi, John P

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Mechanical testing for Pyroceram (trademark) 9606 glass-ceramic fabricated by Corning was conducted to determine mechanical properties of the material including slow crack growth.Valid testing was not achieved in tension, compression, and shear testing due to inappropriate test specimen configurations provided and primarily due to the existence of fortified layer( in tension).

Topics: BOUNDARY CONDITIONS, DIRECT NUMERICAL SIMULATION, GALERKIN METHOD, DECOMPOSITION, PERFECTLY MATCHED...

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219

Jun 12, 2011
06/11

by
Nelson, R. M.; Buratti, B. J; Brown, R. H.; Hapke, B. W.; Smythe, W. D.; Kamp, L.; Boryta, M.; Baines, K. H.; Bellucci, G.; Bibring, J.-P.

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We present preliminary evidence that suggests a hemispheric albedo dichotomy on Titan, the largest planetary satellite in the Solar System. We have also studied the photometric properties of several dark circular features on Titan's surface to test if they might be of impact origin. The evidence is derived from photometric analysis of selected surface regions taken at different Titanian longitudes and solar phase angles using images from the Cassini Saturn Orbiter Visual and Infrared Mapping...

Topics: TURBULENT FLOW, LARGE EDDY SIMULATION, EQUILIBRIUM FLOW, NAVIER-STOKES EQUATION, FLOW DISTORTION,...

A document discusses work that obtains a low-dimensional model that captures both temporal and spatial flow by constructing spatial and temporal four-mode models for two classic flow problems. The models are based on the proper orthogonal decomposition at two reference Reynolds numbers. Model predictions are made at an intermediate Reynolds number and compared with direct numerical simulation results at the new Reynolds number.

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, FLUID FLOW, DECOMPOSITION,...

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234

Jun 1, 2011
06/11

by
Erickson, Gary M

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The goal of this project is to determine precursors and signatures of local substorm onset and how they evolve in the plasma sheet using the Geotail near-Earth database. This project is part of an ongoing investigation involving this PI, Nelson Maynard (Mission Research Corporation), and William Burke (AFRL) toward an empirical understanding of the onset and evolution of substorms. The first year began with dissemination of our CRRES findings, which included an invited presentation and major...

Topics: GEOMAGNETIC TAIL, TURBULENCE MODELS, MAGNETOHYDRODYNAMIC TURBULENCE, DIRECT NUMERICAL SIMULATION,...

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240

May 31, 2011
05/11

by
Ning, Cun-Zhen

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Multimode beating was greatly enhanced by taking output from part (e.g., half) of the output facet. Simpler sources of microwaves and millimeter waves of various frequencies were generated by varying the VCSEL diameter in a single multimode VCSEL our coupling of a few VCSELs. Breathing frequency in multi-mode operations affects modulation response and bandwidth. Optimizing RO frequency and mode beating frequency could potentially expand bandwidths suitable for wide band digital communications.

Topics: DIRECT NUMERICAL SIMULATION, JET AIRCRAFT NOISE, SUPERSONIC JET FLOW, TURBULENT JETS, PARALLEL...

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569

Jun 1, 2011
06/11

by
Ginsburg, Ambrose; Creagh, John W. R.; Ritter, William K

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An investigation was conducted on a large centrifugal compressor from an experimental turbojet engine to determine the performance of the compressor and to obtain fundamental information on the aerodynamic problems associated with large centrifugal-type compressors. The results of the research conducted on the compressor indicated that the compressor would not meet the desired engine-design air-flow requirements (78 lb/sec) because of an air-flow restriction in the vaned collector (diffuser)....

Topics: RESONATORS, DIRECT NUMERICAL SIMULATION, FLOW DISTRIBUTION, SLITS, ACOUSTIC IMPEDANCE, WHITE NOISE,...

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113

May 31, 2011
05/11

by
NON

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The BioScan System was developed by OmniCorder Technologies, Inc. at the Jet Propulsion Laboratory. The system is able to locate cancerous lesions by detecting the cancer's ability to recruit a new blood supply. A digital sensor detects infrared energy emitted from the body and identifies the minute differences accompanying the blood flow changes associated with cancerous cells. It also has potential use as a monitoring device during cancer treatment. This technology will reduce the time taken...

Topics: ALGORITHMS, COMBINATORIAL ANALYSIS, OPTIMIZATION, QUANTUM COMPUTATION, ADIABATIC EQUATIONS,...

This study examined the effect a variety of induced velocity shears had on salt finger formation. Two harmonic, single frequency velocity profiles were utilized under varied shear strength and angular frequency. The third multi-frequency experiment employed a stochastic shear wave field. This model used frequencies that conformed to the GM spectral model for internal waves with an initial random phase distribution, modeling an environment representative of typical oceanic conditions. These...

Topics: Double Diffusion, Salt Fingers, Density Ratio, Richardson Number, Direct Numerical Simulation,...

Mobility architectures that place complexity in end nodes rather than in the network interior have many advantageous properties and are becoming popular research topics. Such architectures typically push mobility support into higher layers of the protocol stack than network layer approaches like Mobile IP. The literature is ripe with proposals to provide mobility services in the transport, session, and application layers. In this paper, we focus on a mobility architecture that makes the most...

Topics: NASA Technical Reports Server (NTRS), COMPUTER NETWORKS, DIRECT NUMERICAL SIMULATION, PROTOCOL...

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171

May 6, 2010
05/10

by
Andrews, Jane C.; Knowlton, Kell

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Light pollution has significant adverse biological effects on humans, animals, and plants and has resulted in the loss of our ability to view the stars and planets of the universe. Over half of the U.S. population resides in coastal regions where it is no longer possible to see the stars and planets in the night sky. Forty percent of the entire U.S. population is never exposed to conditions dark enough for their eyes to convert to night vision capabilities. In coastal regions, urban lights...

Topics: BOUNDARY LAYERS, WALLS, WIND TUNNELS, HIGH SPEED, STABILITY TESTS, HIGH FREQUENCIES, MACH NUMBER,...

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201

May 27, 2011
05/11

by
Yegenoglu, F.; Inukai, T.; Kaplan, T.; Redman, W.; Mitchell, C

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Future satellite communications is expected to be fully integrated into National and Global Information Infrastructures (NII/GII). These infrastructures will carry multi gigabit-per-second data rates, with integral switching and routing of constituent data elements. The satellite portion of these infrastructures must, therefore, be more than pipes through the sky. The satellite portion will also be required to perform very high speed routing and switching of these data elements to enable...

Topics: DIRECT NUMERICAL SIMULATION, MIXING LAYERS (FLUIDS), GAS JETS, TURBULENT FLOW, GALERKIN METHOD,...

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273

May 30, 2011
05/11

by
Braun, Scott A

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A numerical simulation of Hurricane Bob (1991) is conducted using the Penn State University-National Center for Atmospheric Research mesoscale model MM5 with a horizontal grid spacing of 1.3 Km on the finest nested mesh The model produces a realistic hurricane that intensifies slowly during the period of fine-scale simulation. Time-averaged results reveal the effects of storm motion. vertical shear, beta gyres and deformation forcing on the structure of radial inflow, vertical motion, and...

Topics: TURBULENCE MODELS, HIGH REYNOLDS NUMBER, AERODYNAMIC CONFIGURATIONS, FLOW VELOCITY, REYNOLDS...

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281

May 31, 2011
05/11

by
Lesley, Michael W.; Anderson, Erin L

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In this paper we discuss the role of surface-sensitive spectroscopy (electron spectroscopy for chemical analysis, or ESCA) in the selection of solvents to replace 1,1,1-trichloroethane in handwipe cleaning of bonding surfaces on NASA's Space Shuttle Reusable Solid Rocket Motor (RSRM). Removal of common process soils from a wide variety of metallic and polymeric substrates was characterized. The cleaning efficiency was usually more dependent on the type of substrate being cleaned and the...

Topics: DIRECT NUMERICAL SIMULATION, FLOW DISTRIBUTION, ENERGY BUDGETS, KINETIC ENERGY, PRESSURE GRADIENTS,...

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384

Jun 9, 2011
06/11

by
Neuhart, Dan H.; McGinley, Catherine B

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An investigation was conducted using hot-wire anemometry to determine the turbulence intensity levels in the test section of the Langley 14- by 22-Foot Subsonic Tunnel in the closed or walls-down configuration. This study was one component of the three-dimensional High-Lift Flow Physics experiment designed to provide code validation data. Turbulence intensities were measured during two stages of the study. In the first stage, the free-stream turbulence levels were measured before and after a...

Topics: COMPUTERS, TURBULENCE, VISCOUS FLOW, DIRECT NUMERICAL SIMULATION, HYPERCUBE MULTIPROCESSORS,...

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305

May 28, 2011
05/11

by
Rodgers, Edward B.; Adler, Robert F.; Pierce, Harold F

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Tropical cyclone monthly rainfall amounts are estimated from passive microwave satellite observations for an eleven year period. These satellite-derived rainfall amounts are used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the North Pacific Ocean total rainfall during June-November when tropical cyclones are most important. To estimate these tropical cyclone rainfall amounts, mean monthly rain rates are derived from...

Topics: TAYLOR SERIES, CONVERGENCE, TRANSFER FUNCTIONS, APPROXIMATION, LARGE EDDY SIMULATION, DIRECT...

This algorithm provides a new way to improve the accuracy and asymptotic behavior of a low-dimensional system based on the proper orthogonal decomposition (POD). Given a data set representing the evolution of a system of partial differential equations (PDEs), such as the Navier-Stokes equations for incompressible flow, one may obtain a low-dimensional model in the form of ordinary differential equations (ODEs) that should model the dynamics of the flow. Temporal sampling of the direct numerical...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, DECOMPOSITION, STABILIZATION, ORTHOGONALITY,...

Motivated by a recent survey of experimental data, we examine data on the Kolmogorov spectrum constant in numerical simulations of isotropic turbulence, using results both from previous studies and from new direct numerical simulations over a range of Reynolds numbers (up to 240 on the Taylor scale) at grid resolutions up to 512(exp 3). It is noted that in addition to k(exp -5/3) scaling, identification of a true inertial range requires spectral isotropy in the same wavenumber range. We found...

Topics: NASA Technical Reports Server (NTRS), ISOTROPIC TURBULENCE, DIRECT NUMERICAL SIMULATION, KOLMOGOROV...

In situ observations indicate that the dynamical processes in the geoplasma environment generally entail localized intermittent processes and anomalous global transports. It was suggested by T. Chang that instead of considering the turbulence as a mixture of interacting waves, such type of patchy intermittency could be more easily understood in terms of the development, interaction, merging, preferential acceleration and evolution of coherent magnetic structures. In this three-year project, we...

Topics: NASA Technical Reports Server (NTRS), GEOMAGNETIC TAIL, TURBULENCE MODELS, MAGNETOHYDRODYNAMIC...

The reasearch focused on two areas; (a) the dynamics of forced turbulent flows and (b) time filtered Large Eddy Simulations (TLES). The dynamics of turbulent flows arising from external forcing of the turbulence are poorly understood. In particular, here are many unanswered questions relating the basic dynamical balances and the existence or nonexistence of statistical equilibrium of forced turbulent flows. This research used rapid distortion theory and direct numerical simulations to explore...

Topics: NASA Technical Reports Server (NTRS), TURBULENT FLOW, LARGE EDDY SIMULATION, EQUILIBRIUM FLOW,...

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182

Jun 12, 2011
06/11

by
How, Jonathan P

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The final report for the Orion-II project is taken from Chapter 5 of ''CDGPS-Based Relative Navigation for Multiple Spacecraft,'' a thesis by Megan Mitchell submitted to the MIT Department of Aeronautics and Astronautics, June 2004. This chapter begins with a comparison of the simulation architecture for the original and current simulation setups. Next, the changes made to the individual components of the navigation system are described. Finally, tests performed with a Spirent Simulator at NASA...

Topics: COMPUTERIZED SIMULATION, ACOUSTICS, NAVIER-STOKES EQUATION, TURBULENCE MODELS,...

The research focused on two areas: (a) the dynamics of forced turbulent flows and (b) time filtered Large Eddy Simulations (TLES). The dynamics of turbulent flows arising from external forcing of the turbulence are poorly understood. In particular, here are many unanswered questions relating the basic dynamical balances and the existence or nonexistence of statistical equilibrium of forced turbulent flows. The research used direct numerical simulations to explore these questions. The properties...

Topics: NASA Technical Reports Server (NTRS), TRANSITION FLOW, TURBULENT FLOW, LARGE EDDY SIMULATION,...

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206

Jun 9, 2011
06/11

by
Turso, James; Lawrence, Charles; Litt, Jonatha

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The development of a wavelet-based feature extraction technique specifically targeting FOD-event induced vibration signal changes in gas turbine engines is described. The technique performs wavelet analysis of accelerometer signals from specified locations on the engine and is shown to be robust in the presence of significant process and sensor noise. It is envisioned that the technique will be combined with Kalman filter thermal/health parameter estimation for FOD-event detection via...

Topics: DIRECT NUMERICAL SIMULATION, PARALLEL PROCESSING (COMPUTERS), COMPUTATIONAL FLUID DYNAMICS,...

This viewgraph presentation reviews direct numerical simulation in the late stages of the transition process to turbulence.

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, TURBULENCE, BOUNDARY LAYER...

The objective of this work was to use direct numerical simulation (DNS) techniques to study the physics of noise generation by a high-speed turbulent jet. A Mach 0.9, Reynolds number 3,600 jet was selected because of available experimental data. New numerical methods for generating disturbances at the nozzle and computing far-field sound were developed and reported in the course of this work. Over 25 million mesh points were used in the simulations which ran for over 50,000 timesteps and...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, JET AIRCRAFT NOISE, SUPERSONIC...

The interest in transitional/turbulent wakes spans the spectrum from an intellectual pursuit to understand the complex underlying physics to a critical need in aeronautical engineering and other disciplines to predict component/system performance and reliability. Cylinder wakes have been studied extensively over several decades to gain a better understanding of the basic flow phenomena that are encountered in such flows. Experimental, computational and theoretical means have been employed in...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, TURBULENT WAKES, CYLINDRICAL...

A report presents a study addressing the question of which large-eddy simulation (LES) equations are appropriate for modeling the flow of evaporating drops of a multicomponent liquid in a gas (e.g., a spray of kerosene or diesel fuel in air). The LES equations are obtained from the direct numerical simulation (DNS) equations in which the solution is computed at all flow length scales, by applying a spatial low-pass filter. Thus, in LES the small scales are removed and replaced by terms that...

Topics: NASA Technical Reports Server (NTRS), LARGE EDDY SIMULATION, FUEL FLOW, LOW PASS FILTERS, GAS...

Results of an ongoing effort to quantify the role turbulence in scattering sound in jets are reported. Using a direct numerical simulation database to provide the flow data, ray paths traced through the mean flow are compared with those traced through the actual time evolving turbulent flow. Significant scattering by the turbulence is observed. The most notable effect is that upstream traveling waves that are trapped in the potential core by the mean flow, which acts as a wave guide, easily...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, RAY TRACING, TURBULENCE,...

A method of parameterizing the coefficients of a dynamical system based of a proper orthogonal decomposition (POD) representing the flow dynamics of a viscous fluid has been introduced. (A brief description of POD is presented in the immediately preceding article.) The present parameterization method is intended to enable construction of the dynamical system to accurately represent the temporal evolution of the flow dynamics over a range of Reynolds numbers. The need for this or a similar...

Topics: NASA Technical Reports Server (NTRS), COEFFICIENTS, DECOMPOSITION, PARAMETERIZATION, DYNAMICAL...

We present a discrete analysis of non-reflecting boundary conditions for the discontinuous Galerkin method. The boundary conditions considered in this paper include the recently proposed Perfectly Matched Layer absorbing boundary condition for the linearized Euler equation and two non-reflecting boundary conditions based on the characteristic decomposition of the flux on the boundary. The analyses for the three boundary conditions are carried out in a unifled way. In each case, eigensolutions...

Topics: NASA Technical Reports Server (NTRS), BOUNDARY CONDITIONS, DIRECT NUMERICAL SIMULATION, GALERKIN...

Importance of this work: (1) This is the first work to model electron-phonon scattering within a quantum mechanical approach to nanotransistors. The simulations use the non equilibrium Green's function method. (2) A simple equation which captures the importance of scattering as a function of the spatial location from source to drain is presented. This equation helps interpret the numerical simulations. (3) We show that the resistance per unit length in the source side is much larger than in the...

Topics: NASA Technical Reports Server (NTRS), ELECTRON SCATTERING, MATHEMATICAL MODELS, TRANSISTORS,...

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191

May 31, 2011
05/11

by
Allen, Michael J.; Ryan, Jack; Hanson, Curtis E.; Parle, James F

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String stability analysis of an autonomous formation flight system was performed using linear and nonlinear simulations. String stability is a measure of how position errors propagate from one vehicle to another in a cascaded system. In the formation flight system considered here, each i(sup th) aircraft uses information from itself and the preceding ((i-1)(sup th)) aircraft to track a commanded relative position. A possible solution for meeting performance requirements with such a system is to...

Topics: FIELD-PROGRAMMABLE GATE ARRAYS, DIRECT NUMERICAL SIMULATION, PROGRAMMING LANGUAGES, EVOLVABLE...

High-order methods are quickly becoming popular for turbulent flows as the amount of computer processing power increases. The flux reconstruction (FR) method presents a unifying framework for a wide class of high-order methods including discontinuous Galerkin (DG), Spectral Difference (SD), and Spectral Volume (SV). It offers a simple, efficient, and easy way to implement nodal-based methods that are derived via the differential form of the governing equations. Whereas high-order methods have...

Topics: NASA Technical Reports Server (NTRS), GALERKIN METHOD, TURBULENT FLOW, NONLINEARITY, DISCONTINUITY,...

A localized 3-D roughness causes boundary-layer separation and (weak) shocks. Most importantly, streamwise vortices occur which induce streamwise (low U, high T) streaks. Immersed boundary method (volume force) suitable to represent roughness element in DNS. Favorable comparison between bi-global stability theory and DNS for a "y-mode" Outlook: Understand the flow physics (investigate "z-modes" in DNS through sinuous spanwise forcing, study origin of the beat in DNS).

Topics: NASA Technical Reports Server (NTRS), BOUNDARY LAYER SEPARATION, SURFACE ROUGHNESS, DIRECT...

The objectives of this project are to perform direct numerical simulation of the micro-fluid and acoustic fields of a resonant acoustic liner and to investigate the physical processes by which incident sound waves are damped by the acoustic liner. We would like to report that our research work and results have fulfilled both objectives of the grant. The following is a summary of the important accomplishments: (1) Two dimensional direct numerical simulation of the flow and acoustic field around...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, FLUID DYNAMICS, IMPEDANCE...

This study assesses an explicit algebraic Reynolds stress turbulence model in the in the three-dimensional Reynolds averaged Navier-Stokes (RANS) solver, ISAAC (Integrated Solution Algorithm for Arbitrary Con gurations). Additionally, it compares solutions for two select configurations between ISAAC and the RANS solver PAB3D. This study compares with either direct numerical simulation data, experimental data, or empirical models for several different geometries with compressible, separated, and...

Topics: NASA Technical Reports Server (NTRS), COMPUTATIONAL FLUID DYNAMICS, REYNOLDS STRESS, NAVIER-STOKES...

The present investigation is a continuation of a previous joint project between the Florida State University and the NASA Langley Research Center Liner Physics Team. In the previous project, a study of acoustic liners, in two dimensions, inside a normal incidence impedance tube was carried out. The study consisted of two parts. The NASA team was responsible for the experimental part of the project. This involved performing measurements in an impedance tube with a large aspect ratio slit...

Topics: NASA Technical Reports Server (NTRS), LININGS, MATHEMATICAL MODELS, AEROACOUSTICS, COMPUTATIONAL...

Two phase flows can be found in broad situations in nature, biology, and industry devices and can involve diverse and complex mechanisms. While the physical models may be specific for certain situations, the mathematical formulation and numerical treatment for solving the governing equations can be general. Hence, we will require information concerning each individual phase as needed in a single phase. but also the interactions between them. These interaction terms, however, pose additional...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, COMPUTATIONAL FLUID DYNAMICS,...

A method of calculation is presented that allows the simulation of the time-dependent three-dimensional motion of thin liquid layers on solid substrates for systems with finite equilibrium contact angles. The contact angle is a prescribed function of position on the substrate. Similar mathematical models are constructed for substrates with a pattern of roughness. Evolution equations are given, using the lubrication approximation, that include viscous, capillary and disjoining forces. Motion to...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, DROPS (LIQUIDS), MATHEMATICAL...

A spatially developing direct numerical simulation has been performed for flow over a flat plate that is subjected to a one-time fluid injection through an elongated slit in the wall. The flow parameters have been chosen to closely approximate the experimental conditions of Haidari, Taylow, and Smith (AIAA-89-0964). A hairpin vortex quickly develops near the upstream end of the slit, and a pair of necklace vortices form around the slow-moving injection fluid. As seen in the experiments and...

Topics: NASA Technical Reports Server (NTRS), HORSESHOE VORTICES, DIRECT NUMERICAL SIMULATION, BOUNDARY...

Tests are conducted on a quad-redundant fault tolerant flight control computer to establish upset characteristics of an avionics system in an electromagnetic field. A numerical simulation and statistical model are described in this work to analyze the open loop experiment data collected in the reverberation chamber at NASA LaRC as a part of an effort to examine the effects of electromagnetic interference on fly-by-wire aircraft control systems. By comparing thousands of simulation and model...

Topics: NASA Technical Reports Server (NTRS), ELECTROMAGNETIC FIELDS, STATISTICAL ANALYSIS, RADIATION...

We study both analytically and numerically the complexity of the adiabatic quantum evolution algorithm applied to random instances of combinatorial optimization problems. We use as an example the NP-complete set partition problem and obtain an asymptotic expression for the minimal gap separating the ground and exited states of a system during the execution of the algorithm. We show that for computationally hard problem instances the size of the minimal gap scales exponentially with the problem...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, COMBINATORIAL ANALYSIS, OPTIMIZATION, QUANTUM...

The results of an asymptotic theory for statistical closures for compressible turbulence are explored and validated with the direct numerical simulation of the isotropic decay and the homogeneous shear. An excellent collapse of the data is seen. The slow portion is found to scale, as predicted by the theory, with the quantity M(sub t)(sup 2) and epsilon(sub s). The rapid portion has an unambiguous scaling with alpha(sup 2)M(sub t)(sup s)epsilon(sub s)[P(sub k)/epsilon - l](Sk/epsilon)(sup 2)....

Topics: NASA Technical Reports Server (NTRS), COMPRESSIBILITY, TURBULENCE, DIRECT NUMERICAL SIMULATION,...

The purpose of this work is twofold. First, given the computational resources available today, it is possible to reach, using DNS, higher Reynolds numbers than in Briggs et al.. In the present study, the microscale Reynolds numbers reached in the low- and high-energy homogeneous regions are, respectively, 32 and 69. The results reported earlier can thus be complemented and their robustness in the presence of increased turbulence studied. The second aim of this work is to perform a detailed and...

Topics: NASA Technical Reports Server (NTRS), DIRECT NUMERICAL SIMULATION, LARGE EDDY SIMULATION, SHEAR...

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330

Jun 1, 2011
06/11

by
Edwards, David; Hubbs, Whitney; Stanaland, Tesia; Altstatt, Richar

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The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) is concentrating research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A sail operates on the principle that photons, originating from the sun, impart pressure and provide a source of spacecraft propulsion. The pressure can be increased, by a factor of two if the sun-facing surface is...

Topics: UPWIND SCHEMES (MATHEMATICS), DIRECT NUMERICAL SIMULATION, COMPUTATIONAL FLUID DYNAMICS,...

A paper describes direct numerical simulations (DNSs) of three-dimensional mixing-layer flows undergoing transition to turbulence; the mixing layers may or may not be laden with evaporating liquid drops.

Topics: NASA Technical Reports Server (NTRS), MIXING LAYERS (FLUIDS), THREE DIMENSIONAL FLOW, TURBULENCE,...

Direct numerical simulation is used to investigate the transition induced by threedimensional isolated roughness elements in a supersonic boundary layer at a free stream Mach number of 3.5. Simulations are performed for two different configurations: one is a square planform roughness and the other is a diamond planform roughness. The mean-flow calculations show that the roughness induces counter rotating streamwise vortices downstream of the roughness. These vortices persist for a long distance...

Topics: NASA Technical Reports Server (NTRS), SURFACE ROUGHNESS, BOUNDARY LAYER TRANSITION, SUPERSONIC...

A program sponsored by the National Aeronautics and Space Administration (NASA) for the investigation of the heat transfer in the transition region of turbine vanes and blades with the object of improving the capability for predicting heat transfer is described,. The accurate prediction of gas-side heat transfer is important to the determination of turbine longevity, engine performance and developmental costs. The need for accurate predictions will become greater as the operating temperatures...

Topics: NASA Technical Reports Server (NTRS), HEAT TRANSFER, TURBINE BLADES, TURBINE ENGINES, TURBULENCE,...