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  • 1
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    Fluid Dynamics of Small, Rugged Vacuum Pumps of Viscous-Drag Type (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: The need to identify spikes in the concentration of hazardous gases during countdowns to space shuttle launches has led Kennedy Space Center to acquire considerable expertise in the design, construction, and operation of special-purpose gas analyzers of mass-spectrometer type. If such devices could be miniaturized so as to fit in a small airborne package or backpack them their potential applications would include integrated vehicle health monitoring in later-generation space shuttles and in hazardous material detection in airports, to name two examples. The bulkiest components of such devices are vacuum pumps, particularly those that function in the low vacuum range. Now some pumps that operate in the high vacuum range (e.g. molecular-drag and turbomolecular pumps) are already small and rugged. The present work aims to determine whether, on physical grounds, one may or may not adopt the molecular-drag principle to the low-vacuum range (in which case viscous-drag principle is the appropriate term). The deliverable of the present effort is the derivation and justification of some key formulas and calculation methods for the preliminary design of a single-spool, spiral-channel viscous-drag pump.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 2002 Research Reports: NASA/ASEE Fellowship Program; 139-148; NASA/CR-2002-211181
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  • 2
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    Thermodynamic Behavior of Nano-sized Gold Clusters on the (001) Surface (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We have studied thermal expansion of the surface layers of the hexagonally reconstructed Au (001) surface using a classical Molecular Dynamics (MD) simulation technique with an Embedded Atomic Method (EAM) type many-body potential. We find that the top-most hexagonal layer contracts as temperature increases, whereas the second layer expands or contracts depending on the system size. The magnitude of expansion coefficient of the top layer is much larger than that of the other layers. The calculated thermal expansion coefficients of the top-most layer are about -4.93 x 10(exp -5)Angstroms/Kelvin for the (262 x 227)Angstrom cluster and -3.05 x 10(exp -5)Angstroms/Kelvin for (101 x 87)Angstrom cluster. The Fast Fourier Transform (FFT) image of the atomic density shows that there exists a rotated domain of the top-most hexagonal cluster with rotation angle close to 1 degree at temperature T less than 1000Kelvin. As the temperature increases this domain undergoes a surface orientational phase transition. These predictions are in good agreement with previous phenomenological theories and experimental studies.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2001-211014 , NAS 1.26:211014 , ICASE-2001-17 , ICCN 2001 Conference; Jan 01, 2001; United States
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  • 3
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    Software for Refining or Coarsening Computational Grids (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A computer program performs calculations for refinement or coarsening of computational grids of the type called "structured" (signifying that they are geometrically regular and/or are specified by relatively simple algebraic expressions). This program is designed to facilitate analysis of the numerical effects of changing structured grids utilized in computational fluid dynamics (CFD) software. Unlike prior grid-refinement and -coarsening programs, this program is not limited to doubling or halving: the user can specify any refinement or coarsening ratio, which can have a noninteger value. In addition to this ratio, the program accepts, as input, a grid file and the associated restart file, which is basically a file containing the most recent iteration of flow-field variables computed on the grid. The program then refines or coarsens the grid as specified, while maintaining the geometry and the stretching characteristics of the original grid. The program can interpolate from the input restart file to create a restart file for the refined or coarsened grid. The program provides a graphical user interface that facilitates the entry of input data for the grid-generation and restart-interpolation routines.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/NP-2002-10-00035-SSC , SSC-00167-SM
    Format: text
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  • 4
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    Nucleation of Quantized Vortices from Rotating Superfluid Drops (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The long-term goal of this project is to study the nucleation of quantized vortices in helium II by investigating the behavior of rotating droplets of helium II in a reduced gravity environment. The objective of this ground-based research grant was to develop new experimental techniques to aid in accomplishing that goal. The development of an electrostatic levitator for superfluid helium, described below, and the successful suspension of charged superfluid drops in modest electric fields was the primary focus of this work. Other key technologies of general low temperature use were developed and are also discussed.
    Keywords: Fluid Mechanics and Thermodynamics
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  • 5
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    Computational Analysis of Cryogenic Flow Through a Control Valve (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The initial efforts to develop the capability to model valves used in rocket engine component testing at Stennis Space Center are documented. An axisymmetric model of a control valve with LN2 as the working fluid was developed. The goal was to predict the effect of change in the plug/sear region of the valve prior to testing. The valve flow coefficient was predicted for a range of plug positions. Verification of the calculations was carried out to quantify the uncertainty in the numerical answer. The modeled results compared well qualitatively to experimental trends. Additionally, insights into the flow processes in the valve were obtained. Benefits from the verification process included the ability to use coarser grids and insight into ways to reduce computational time by using double precision accuracy and non-integer grid ratios. Future valve modeling activities will include shape optimization of the valve/seat region and dynamic grid modeling.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: SE-2003-06-00044-SSC , Proceedings of FEDSM''03 4th ASME-JSME Joint Fluids Engineering Conference; Jul 06, 2003 - Jul 11, 2003; Honolulu, HI; United States
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  • 6
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    Progress in Valve Modeling at Stennis Space Center (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Understanding valve behavior will aid testing of rocket components at Stennis Space Center. The authors of this viewgraph presentation have developed a computational model for a cryogenic liquid control valve, and a gas pressure regulator valve. The model is a compressible/incompressible pressure-based FDNS code from Marshall Space Flight Center (MSFC). It is a k-epsilon turbulence model with wall functions.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: SE-2002-12-00081-SSC , 14th Annual Symposium on Propulsion; Dec 10, 2002 - Dec 11, 2002; State College, PA; United States
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  • 7
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    Computational and Experimental Flow Field Analyses of Separate Flow Chevron Nozzles and Pylon Interaction (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A computational and experimental flow field analyses of separate flow chevron nozzles is presented. The goal of this study is to identify important flow physics and modeling issues required to provide highly accurate flow field data which will later serve as input to the Jet3D acoustic prediction code. Four configurations are considered: a baseline round nozzle with and without a pylon, and a chevron core nozzle with and without a pylon. The flow is simulated by solving the asymptotically steady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, up-wind, flux-difference splitting finite volume scheme and standard two-equation kappa-epsilon turbulence model with a linear stress representation and the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. The current CFD results are seen to be in excellent agreement with Jet Noise Lab data and show great improvement over previous computations which did not compensate for enhanced mixing due to high temperature gradients.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 2003-3212 , 9th AIAA/CEAS Aeroacoustics Conference and Exhibition; May 12, 2003 - May 14, 2003; Hilton Head, SC; United States
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  • 8
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    Fluid Dynamics of a Pressure Reducing Inlet (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Instruments for the monitoring of hazardous gases in and near the space shuttle collect sample gas at pressures on the order of one atmosphere and analyze their properties in an ultra-high vacuum by means of a quadrupole-mass-spectrometer partial pressure transducer. Sampling systems for such devices normally produce the required pressure reduction through combinations of vacuum pumps, fluid Tees and flow restrictors (e.g. orifices, sintered metal frits or capillaries). The present work presents an analytical model of the fluid dynamics of such a pressure reduction system which enables the calculation of the pressure in the receiver vessal in terms of system parameters known from the specifications for a given system (e.g. rated pumping speeds of the pumping hardware and the diameters of two orifices situated in two branches of a fluid Tee). The resulting formulas will expedite the fine tuning of instruments now under development and the design of later generations of such devices.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/ASEE Summer Faculty Fellowship Program; 161-169; NASA/CR-2001-210265
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