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  • 1
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    Plastic biochannel hybridization devices: a new concept for microfluidic DNA arrays (2002)
    Elsevier
    Details
    Publication Date: 2002-12-01
    Print ISSN: 0003-2697
    Electronic ISSN: 1096-0309
    Topics: Biology , Chemistry and Pharmacology
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Developments in Impeller/Seal Secondary Flow Path Modeling for Dynamic Force Coefficients and Leakage (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper highlights bulk flow and CFD-based models prepared to calculate force and leakage properties for seals and shrouded impeller leakage paths. The bulk flow approach uses a Hir's based friction model and the CFD approach solves the Navier Stoke's (NS) equation with a finite whirl orbit or via analytical perturbation. The results show good agreement in most instances with available benchmarks.
    Keywords: Mechanical Engineering
    Type: Rotordynamic Instability Problems in High-Performance Turbomachinery 1996; 209-228; NASA-CP-3344
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Seal Leakages for Honeycomb or Smooth Configurations (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Three dimensional-CFD simulations were attempted to analyze the flow field in a honeycomb flat plate tester. This discussion reviews some of the numerical difficulties and relations, including those relating the honeycombs to labyrinth throttles and the consistency of selected seal and tester data sets.
    Keywords: Mechanical Engineering
    Type: Rotordynamic Instability Problems in High-Performance Turbomachinery 1996; 281-291; NASA-CP-3344
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Analyses of Control Surface Seal Tested in the Ames Arc Jet Tunnel (Panel Test Facility) (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The contents include: 1) Rope Seal; 2) Improvements to porous medial simulation in CFD-ACE+; 3) Porous media heat transfer validation case-stead-state and transient flat plate; 4) Simulation of GRC cold flow seal test fixture; 5) Simulation of calibration plate in the Panel Test Facility (PTF); and 6) Simulation of rope seal test in the PTF. This paper is in viewgraph form.
    Keywords: Mechanical Engineering
    Type: 2001 NASA Seal/Secondary Air System Workshop; Volume 1; 315-339; NASA/CP-2002-211911/VOL1
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    SCISEAL: A CFD code for analysis of fluid dynamic forces in seals (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A viewgraph presentation is made of the objectives, capabilities, and test results of the computer code SCISEAL. Currently, the seal code has: a finite volume, pressure-based integration scheme; colocated variables with strong conservation approach; high-order spatial differencing, up to third-order; up to second-order temporal differencing; a comprehensive set of boundary conditions; a variety of turbulence models and surface roughness treatment; moving grid formulation for arbitrary rotor whirl; rotor dynamic coefficients calculated by the circular whirl and numerical shaker methods; and small perturbation capabilities to handle centered and eccentric seals.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center, Seals Flow Code Development 1993; p 35-58
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Development of a CFD Code for Analysis of Fluid Dynamic Forces in Seals (1991)
    In:  CASI
    Details
    Publication Date: 2014-09-23
    Description: The aim is to develop a 3-D computational fluid dynamics (CFD) code for the analysis of fluid flow in cylindrical seals and evaluation of the dynamic forces on the seals. This code is expected to serve as a scientific tool for detailed flow analysis as well as a check for the accuracy of the 2D industrial codes. The features necessary in the CFD code are outlined. The initial focus was to develop or modify and implement new techniques and physical models. These include collocated grid formulation, rotating coordinate frames and moving grid formulation. Other advanced numerical techniques include higher order spatial and temporal differencing and an efficient linear equation solver. These techniques were implemented in a 2D flow solver for initial testing. Several benchmark test cases were computed using the 2D code, and the results of these were compared to analytical solutions or experimental data to check the accuracy. Tests presented here include planar wedge flow, flow due to an enclosed rotor, and flow in a 2D seal with a whirling rotor. Comparisons between numerical and experimental results for an annular seal and a 7-cavity labyrinth seal are also included.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Seals Flow Code Development; p 27-39
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Comparison of Numerical Results and Multicavity Purge and Rim Seal Data with Extensions to Dynamics (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The computation of flows within interconnected, multiple-disk cavities shows strong interaction between the cavities and the power stream. For this reason, simulations of single cavities in such cases are not realistic; the complete, linked configuration must be considered. Unsteady flow fields affect engine stability and can engender power-stream-driven secondary flows that produce local hot spotting or general cavity heating. Further, a concentric whirling rotor produces a circumferential pressure wave, but a statically eccentric whirling rotor produces a radial wave; both waves affect cavity ingestion and the stability of the entire engine. It is strongly suggested that seals be used to enhance turbojet engine stability. Simple devices, such as swirl brakes, honeycomb inserts, and new seal configurations, should be considered. The cost effectiveness of the NASA Lewis Research Center seals program can be expressed in terms of program goals (e.g., the Integrated High-pressure/Temperature Engine Technology (IHPTET) cannot be achieved without such a program), cost (savings to $250 million/1-percent decrease in specific fuel consumption), and indirect benefits (reduction of atmospheric NO(x) and CO2 and reduction of powerplant downtime).
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106685 , E-9039 , NAS 1.15:106685 , Northern Ohio Technical Symposium, Aerospace Today; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Numerical, analytical, experimental study of fluid dynamic forces in seals (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: NASA/Lewis Research Center is sponsoring a program for providing computer codes for analyzing and designing turbomachinery seals for future aerospace and engine systems. The program is made up of three principal components: (1) the development of advanced three dimensional (3-D) computational fluid dynamics codes, (2) the production of simpler two dimensional (2-D) industrial codes, and (3) the development of a knowledge based system (KBS) that contains an expert system to assist in seal selection and design. The first task has been to concentrate on cylindrical geometries with straight, tapered, and stepped bores. Improvements have been made by adoption of a colocated grid formulation, incorporation of higher order, time accurate schemes for transient analysis and high order discretization schemes for spatial derivatives. This report describes the mathematical formulations and presents a variety of 2-D results, including labyrinth and brush seal flows. Extensions of 3-D are presently in progress.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-189113 , NAS 1.26:189113
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Numerical Investigations of High Pressure Acoustic Waves in Resonators (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: This presentation presents work on numerical investigations of nonlinear acoustic phenomena in resonators that can generate high-pressure waves using acoustic forcing of the flow. Time-accurate simulations of the flow in a closed cone resonator were performed at different oscillation frequencies and amplitudes, and the numerical results for the resonance frequency and fluid pressure increase match the GRC experimental data well. Work on cone resonator assembly simulations has started and will involve calculations of the flow through the resonator assembly with and without acoustic excitation. A new technique for direct calculation of resonance frequency of complex shaped resonators is also being investigated. Script-driven command procedures will also be developed for optimization of the resonator shape for maximum pressure increase.
    Keywords: Acoustics
    Type: 2003 NASA Seal/Secondary Air System Workshop, Volume 1; 273-295; NASA/CP-2004-212963/VOL1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Numerical, Analytical, Experimental Study of Fluid Dynamic Forces in Seals Volume 6: Description of Scientific CFD Code SCISEAL (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2004-213199-VOL6 , NAS 1.26:2004-213199 , E-14708-6
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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