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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1993

Four-Nozzle Benchmark Wind Tunnel Model USA Code Solutions for Simulation of Multiple Rocket Base Flow Recirculation at 145,000 Feet Altitude

Multiple rocket exhaust plume interactions at high altitudes can produce base flow recirculation with attendant alteration of the base pressure coefficient and increased base heating. A search for a good wind tunnel benchmark problem to check grid clustering technique and turbulence modeling turned up the experiment done at AEDC in 1961 by Goethert and Matz on a 4.25-in. diameter domed missile base model with four rocket nozzles. This wind tunnel model with varied external bleed air flow for the base flow wake produced measured p/p(sub ref) at the center of the base as high as 3.3 due to plume flow recirculation back onto the base. At that time in 1961, relatively inexpensive experimentation with air at gamma = 1.4 and nozzle A(sub e)/A of 10.6 and theta(sub n) = 7.55 deg with P(sub c) = 155 psia simulated a LO2/LH2 rocket exhaust plume with gamma = 1.20, A(sub e)/A of 78 and P(sub c) about 1,000 psia. An array of base pressure taps on the aft dome gave a clear measurement of the plume recirculation effects at p(infinity) = 4.76 psfa corresponding to 145,000 ft altitude. Our CFD computations of the flow field with direct comparison of computed-versus-measured base pressure distribution (across the dome) provide detailed information on velocities and particle traces as well eddy viscosity in the base and nozzle region. The solution was obtained using a six-zone mesh with 284,000 grid points for one quadrant taking advantage of symmetry. Results are compared using a zero-equation algebraic and a one-equation pointwise R(sub t) turbulence model (work in progress). Good agreement with the experimental pressure data was obtained with both; and this benchmark showed the importance of: (1) proper grid clustering and (2) proper choice of turbulence modeling for rocket plume problems/recirculation at high altitude.

Dougherty, N. S.↗

NASA NTRS1991

Computational aspects of chemically reacting flows

An implicit, time-dependent approach is taken to solve the inviscid conservative equations in a vertex-based finite-volume formulation. The convective fluxes are estimated by a modified Riemann solver, and higher-order accuracy is obtained by means of the MUSCL. Implicit techniques are adopted to deal with the equation stiffness as a result of the clustered grid and chemical source term. The real-gas Roe matrix and the ADI and LU schemes have been tested on the sample problems: hypersonic flow over blunt configurations, such as the forebody of a double ellipse, and the near wake of a conic aerobrake. Temperature distribution and standoff distance are validated against the shock-fitting, central-differencing results. Equilibrium temperature may be recovered by artificially increasing the chemical rates at the wall. The present method satisfactorily resolves the flow structure, including the strong expansion behind the flat base. The relative merits and performance of the real-gas TVD and implicit schemes are discussed briefly.

Li, C. P.↗

NASA NTRS2009

Cavities of Weak Magnetic Field Strength in the Wake of FTEs: Results from Global Magnetospheric MHD Simulations

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.↗

NASA NTRS1984

Mod-2 wind turbine field operations experience

The Mod-2 wind turbine is now in a 2-year research/experimental operations phase which offers a unique opportunity to study the effects of single and multiple wind turbines interacting with each other, the power grid, and the environment. This paper addresses the field operations and research testing experienced at the Mod-2 Cluster Goodnoe Hills Research Test Site near Goldendale, WA. Field operation, both routine and nonroutine, are discussed as well as the role of the participating utility. Technical areas discussed pertain to system performance and loads. Specific research tests relating to acoustics, TV interference, and wake effects are also discussed.

Gordon, L. H.↗

NASA NTRS1988

Flow Analysis of Space Shuttle Feed Line 17-inch Disconnect Valve

A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle External Tank/Orbiter propellant feed line disconnect flapper valves with upstream elbows. The full Navier-Stokes code, INS3D, is modified to handle interior obstacles. Grids are generated by SVTGD3D code. Two dimensional initial grids in the flow cross section with and without the flappers are improved by elliptic smoothing to provide better orthogonality, clustering and smoothness to the three dimensional grid. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 x 10(exp 6). The results will serve as a guide to improved design and enhanced testing of the disconnect.

Kandula, Max↗

NASA NTRS1987

Space station group activities habitability module study: A synopsis

Space station habitability was studied by investigating crew activity routines, proximities, ergonomic envelopes, and group volumes. Ten alternative schematic interior designs were proposed. Preliminary conclusions include: (1) in-service interior modifications may be necessary and should be planned for; (2) design complexity will be increased if the module cluster is reduced from five to three; (3) the increased crew circulation attendant upon enhancement of space station activity may produce human traffic bottlenecks and should be planned for; (4) a single- or two-person quiet area may be desirable to provide crew members with needed solitude during waking hours; and (5) the decision to choose a two-shift or three-shift daily cycle will have a significant impact on the design configuration and operational efficiency of the human habitat.

Nixon, David↗

NASA NTRS1993

A numerical investigation of a subsonic jet in a crossflow

The flowfield induced by a single, subsonic jet exhausting perpendicularly from a flat plate into a subsonic crossflow has been numerically investigated. The test case was chosen to match available experimental data where the jet Mach number was 0.78, and the freestream Mach number was 0.13. Time-averaged solutions were obtained using the thin-layer Navier-Stokes equations and two overlapping grids. The solutions were sensitive to the radial grid clustering near the edge of the jet and to the far-field boundary conditions. Experimental data comparisons were required to determine the most appropriate jet grid and satisfactory boundary conditions. Globally, the solutions converged in about 6000 iterations. The computational results accurately showed the deflected jet and associated contrarotating vortices. The fine clustered grid in the region upstream of the jet exit allowed the horseshoe vortex in the boundary layer near the jet exit to be captured. Most importantly for aircraft applications, the computed plate pressure distributions compared favorably with the experimental data over most of the surface. However, in the wake region immediately downstream of the jet exit, where there is extensive flow separation, some discrepancies with experimental data were observed. Two turbulence models were used in this study: (1) the zero-equation, two layer Baldwin-Lomax turbulence model; and (2) one-equation Baldwin-Barth turbulence model. The turbulence models gave results which generally compared no better with experimental data than the laminar computation results.

Chiu, Stephen H.↗

NASA NTRS1975

Detection of severe storms by satellites

Ideas are presented for severe storm identification based on satellite data. The tops of huge thunderstorms in satellite pictures often appear as vast areas of extensive cirrus cloud; they consist of clusters of anvil clouds, each generated by vigorous thunderstorm circulation. The overshooting tops observed in satellite pictures are located where the subanvil updrafts are the strongest. Learjet experiment results show that an overshooting top varies either quickly or slowly, depending on the characteristics of individual clouds. When an overshooting top collapses, a small segment of the anvil cirrus jumps upward in the wake of the overshooting top. Also discussed is the monitoring of vertical motions from satellites and tornado-producing thunderstorms from geostationary altitude. A very high-resolution imagery of both infrared and visual spectral bands makes it possible to infer vertical motions beneath the anvil top. A combination of cloud velocity and anvil expansion rate will permit, in the future, determining the location of severe storms within the vast areas of anvil clouds.

Fujita, T. T.↗

NASA NTRS1985

Mod-2 wind turbine field operations experiment

The three-machine, 7.5 MW Goodnoe Hills located near Goldendale, Washington and is now in a research/experimental operations phase that offers a unique opportunity to study the effects of single and multiple wind turbines interacting with each other, the power grid; and the environment. Following a brief description of the turbine and project history, this paper addresses major problem areas and research and development test results. Field operations, both routine and nonroutine, are discussed. Routine operation to date has produced over 13,379,000 KWh of electrical energy during 11,064 hr of rotation. Nonroutine operation includes suspended activities caused by a crack in the low speed shaft that necessitated a redesign and reinstallation of this assembly on all three turbines. With the world's largest cluster back in full operation, two of the turbines will be operated over the next years to determine their value as energy producer. The third unit will be used primarily for conducting research tests requiring configuration changes to better understand the wind turbine technology. Technical areas summarized pertain to system performance and enhancements. Specific research tests relating to acoustics, TV interference, and wake effects conclude the paper.

Gordon, L. H.↗

NASA NTRS1996

Rayleigh scattering measurements in supersonic facilities

Using a narrow-band, pulsed, ArF excimer laser and a single-intensified CCD camera, planar laser Rayleigh scattering measurements were performed to obtain quantitative density measurements both in the free stream and in a model flow field. These measurements were conducted in the 15-inch, Mach 6 high temperature facility at NASA Langley Research Center. This facility is capable of achieving stagnation temperatures up to 700 K (800 F) over a range of stagnation pressures from 0.35 to 2.07 MPa (50 to 300 psia). The high temperature capability of this facility eliminates the clustering effect observed in earlier Mach 6 studies, and allows quantitative density measurements in the free stream over a range of stagnation pressures from 0.35 to 1.75 MPa (50 to 250 psia). Model flow field measurements were obtained on 38.1 mm diameter cylinder. Measurement locations include the free stream, the region behind the bow shock in front of the model, and the region behind the model including the wake. The densities deduced from the Rayleigh scattering measurements in the model flow field are compared with CFD computations. Measurement uncertainties and the detection limit are discussed.

Shirinzadeh, B.↗

NASA NTRS1988

The morphology of multiple-nucleus brightest cluster galaxies

The morphology of high SNR CCD images of 16 multiple-nucleus brightest cluster galaxies is studied using an algorithm that models images of the systems as the line-of-sight superposition of normal elliptical galaxies. The algorithm is applied initially to the classic multiple-nucleus cD galaxy in A2199. Evidence is found suggestive of deep interpenetrating high-speed encounters by its secondaries. The interactions effects studied include noncentric isophotes, brightness profile effects, excess light around primary galaxies, and dynamical friction wakes. The results show that in many cases multiple systems are interacting systems.

Lauer, Tod R.↗

NASA NTRS1992

Fractals and cosmological large-scale structure

Observations of galaxy-galaxy and cluster-cluster correlations as well as other large-scale structure can be fit with a 'limited' fractal with dimension D of about 1.2. This is not a 'pure' fractal out to the horizon: the distribution shifts from power law to random behavior at some large scale. If the observed patterns and structures are formed through an aggregation growth process, the fractal dimension D can serve as an interesting constraint on the properties of the stochastic motion responsible for limiting the fractal structure. In particular, it is found that the observed fractal should have grown from two-dimensional sheetlike objects such as pancakes, domain walls, or string wakes. This result is generic and does not depend on the details of the growth process.

Luo, Xiaochun↗

NASA NTRS1971

Studies of positive-ion composition in the equatorial D-region ionosphere.

Evaluation of two daytime D-region positive-ion composition measurements performed at Thumba, India, for solar zenith angles of 53.2 and 27.8 deg. Comparison of upleg ram with downleg wake data shows a large increase in the concentration of heavy ions 48(+), NO(+) . H2O; 55(+), H3O(+) . (H2O)2; and M(+) greater than 65(+) for the downleg reduced shock condition. Peak concentrations of 48(+) and 55(+) occur at unit optical depth for Lyman alpha radiation. The ion 37(+), H3O(+) . H2O, is dominant for chi = 27.8 deg, but not for chi = 53.2 deg, consistent above 80 km with an origin from the X-ray production of O2(+). Laboratory measurements have shown that the ion, NO(+), can be transferred to heavy hydrates 48(+), 55(+), and M(+) greater than 65(+) by a reaction chain starting with NO(+) + X + M = NO(+) . X + M, where X can be O2, N2, CO2 or a combination of all three, depending on the rate of reaction. This chain, together with a similar reaction scheme starting with O2(+) and ending in 19(+), 37(+), and heavier clusters, is used to provide a consistent explanation for the hydrated ions observed in the D region.

Goldberg, R. A.↗

NASA NTRS1989

Numerical simulation of rotorcraft

The objective of the research is to develop and validate accurate, user-oriented viscous CFD codes (with inviscid options) for three-dimensional, unsteady aerodynamic flows about arbitrary rotorcraft configurations. Unsteady, three-dimensional Euler and Navier-Stokes codes are developed, adapted, and extended to rotor-body combinations. Flow solvers are coupled with zonal grid topologies, including rotating and nonrotating blocks. Special grid clustering and wave-fitting techniques were developed to capture low-level radiating acoustic waves. Significant progress was made in computing the propagation of acoustic waves due to the interaction of a concentrated vortex and a helicopter airfoil. The need for higher-order schemes was firmly established in relatively inexpensive two-dimensional calculations. In three dimensions, the number of grid points required to capture the low-level acoustic waves becomes very large, so that large supercomputer memory becomes essential. Good agreement was obtained between the numerical results obtained with a thin-layer Navier-Stokes code and experimental data from a model rotor. In addition, several nonrotating configurations that are sometimes proposed to simulate rotor blade tips in conventional wind tunnels were examined, and the complex flow around the radical tip shape of the world's fastest helicopter is under investigation. These studies demonstrate the flexibility and power of CFD to gain physical insight, study novel ideas, and examine various possibilities that might be difficult or impossible to set up in physical experiments. As a prelude to studies of rotor-body aerodynamic interactions, a preliminary grid topology and moving-interface strategy were developed. A new Euler/Navier-Stokes code using these techniques computes the vortical wake directly, rather than modeling it, as in most previous rotorcraft studies. Several hover cases were run for conventional and advanced-geometry blades. Numerical schemes using multi-zones and/or adaptive grids appear to be necessary to simulate the complex vortical flows in rotor wakes.

Mccroskey, William J.↗

NASA NTRS2012

Information Systems Coordinate Emergency Management

The rescue crews have been searching for the woman for nearly a week. Hurricane Katrina devastated Hancock County, the southernmost point in Mississippi, and the woman had stayed through the storm in her beach house. There is little hope of finding her alive; the search teams know she is gone because the house is gone. Late at night in the art classroom of the school that is serving as the county s emergency operations center, Craig Harvey is discussing the search with the center s commander. Harvey is the Chief Operating Officer of a unique company called NVision Solutions Inc., based at NASA s Stennis Space Center in Bay St. Louis, only a couple of miles away. He and his entire staff have set up a volunteer operation in the art room, supporting the emergency management efforts using technology and capabilities the company developed through its NASA partnerships. As he talks to the commander, Harvey feels an idea taking shape that might lead them to the woman s location. Working with surface elevation data and hydrological principles, Harvey creates a map showing how the floodwaters from the storm would have flowed along the topography of the region around the woman s former home. Using the map, search crews find the woman s body in 15 minutes. Recovering individuals who have been lost is a sad reality of emergency management in the wake of a disaster like Hurricane Katrina in 2005. But the sooner answers can be provided, the sooner a community s overall recovery can take place. When damage is extensive, resources are scattered, and people are in dire need of food, shelter, and medical assistance, the speed and efficiency of emergency operations can be the key to limiting the impact of a disaster and speeding the process of recovery. And a key to quick and effective emergency planning and response is geographic information. With a host of Earth-observing satellites orbiting the globe at all times, NASA generates an unmatched wealth of data about our ever-changing planet. This information can be captured, analyzed, and visualized by geographic information systems (GIS) to produce maps, charts, and other tools that can reveal information essential to a wide variety of applications including emergency management. Knowing precise, real-time information about the size, location, environmental conditions, and resulting damage of an event like a flood or wildfire as well as the location and numbers of emergency responders and other resources contributes directly to the effectiveness of disaster mitigation. The need for such information is also evident when responding to homeland security threats, such as a terrorist attack. Recognizing the value of its geospatial information resources for this and other purposes, in 1998 Stennis and the state of Mississippi partnered to form what became the Enterprise for Innovative Geospatial Solutions (EIGS) industry cluster, supporting the growth of remote sensing and GIS-based research and business. As part of EIGS, several companies partnered with NASA through dual use and Small Business Innovation Research (SBIR) contracts. Among those was NVision.

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