Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

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greatly improve the fidelity of the engine system simulation and enable the engine system to be ”pre-validated” prior to commitment to engine hardware. Author Component Reliability; Design Analysis; Propulsion System Performance; Computerized Simulation 20000064613 NASA Langley Research Center, Hampton, VA USA Optimization of Car Body under Constraints of Noise, Vibration, and Harshness (NVH), and Crash Kodiyalam, Srinivas, Lockheed Martin Missiles and Space, USA; Yang, Ren-Jye, Ford Research Labs., USA; Sobieszczanski- Sobieski, Jaroslaw, Editor, NASA Ames Research Center, USA; February 2000; In English; See also 20000064579; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document To be competitive on the today’s market, cars have to be as light as possible while meeting the Noise, Vibration, and Harshness (NVH) requirements and conforming to Government-man dated crash survival regulations. The latter are difficult to meet because they involve very compute-intensive, nonlinear analysis, e.g., the code RADIOSS capable of simulation of the dynamics, and the geometrical and material nonlinearities of a thin-walled car structure in crash, would require over 12 days of elapsed time for a single design of a 390K elastic degrees of freedom model, if executed on a single processor of the state-of-the-art SGI Origin2000 computer. of course, in optimization that crash analysis would have to be invoked many times. Needless to say, that has rendered such optimization intractable until now. The car finite element model is shown. The advent of computers that comprise large numbers of concurrently operating processors has created a new environment wherein the above optimization, and other engineering problems heretofore regarded as intractable may be solved. The procedure, shown, is a piecewise approximation based method and involves using a sensitivity based Taylor series approximation model for NVH and a polynomial response surface model for Crash. In that method the NVH constraints are evaluated using a finite element code (MSC/NASTRAN) that yields the constraint values and their derivatives with respect to design variables. The crash constraints are evaluated using the explicit code RADIOSS on the Origin 2000 operating on 256 processors simultaneously to generate data for a polynomial response surface in the design variable domain. The NVH constraints and their derivatives combined with the response surface for the crash constraints form an approximation to the system analysis (surrogate analysis) that enables a cycle of multidisciplinary optimization within move limits. In the inner loop, the NVH sensitivities are recomputed to update the NVH approximation model while keeping the Crash response surface constant. In every outer loop, the Crash response surface approximation is updated, including a gradual increase in the order of the response surface and the response surface extension in the direction of the search. In this optimization task, the NVH discipline has 30 design variables while the crash discipline has 20 design variables. A subset of these design variables (10) are common to both the NVH and crash disciplines. In order to construct a linear response surface for the Crash discipline constraints, a minimum of 21 design points would have to be analyzed using the RADIOSS code. On a single processor in Origin 2000 that amount of computing would require over 9 months! In this work, these runs were carried out concurrently on the Origin 2000 using multiple processors, ranging from 8 to 16, for each crash (RADIOSS) analysis. Another figure shows the wall time required for a single RADIOSS analysis using varying number of processors, as well as provides a comparison of 2 different common data placement procedures within the allotted memories for each analysis. The initial design is an infeasible design with NVH discipline Static Torsion constraint violations of over 10%. The final optimized design is a feasible design with a weight reduction of 15 kg compared to the initial design. This work demonstrates how advanced methodology for optimization combined with the technology of concurrent processing enables applications that until now were out of reach because of very long time-to-solution. Author Concurrent Processing; Design Analysis; Finite Element Method; Mathematical Models; Automobiles; Computerized Simulation; Crashes 20000064625 NASA Marshall Space Flight Center, Huntsville, AL USA Towards Flange-to-Flange Turbopump Simulations for Liquid Rocket Engines Kiris, Cetin, MCAT Inst., USA; Williams, Robert, NASA Marshall Space Flight Center, USA; February 2000; In English; See also 20000064579; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document The primary objective of this research is to support the design of liquid rocket systems for the Advanced Space Transportation System. Since the space launch systems in the near future are likely to rely on liquid rocket engines, increasing the efficiency and reliability of the engine components is an important task. One of the major problems in the liquid rocket engine is to understand fluid dynamics of fuel and oxidizer flows from the fuel tank to plume. Understanding the flow through the entire turbopump geometry through numerical simulation will be of significant value toward design. This will help to improve safety of future space missions. One of the milestones of this effort is to develop, apply and demonstrate the capability and accuracy of 3D CFD methods as efficient design analysis tools on high performance computer platforms. The development of the MPI and MLP versions of the INS3D code is currently underway. The serial version of INS3D code is a multidimensional incompressible Navier-Stokes 92
solver based on overset grid technology. INS3D-MPI is based on the explicit massage-passing interface across processors and is primarily suited for distributed memory systems. INS3D-MLP is based on multi-level parallel method and is suitable for distributed-shared memory systems. For the entire turbopump simulations, moving boundary capability and an efficient time-accurate integration methods are build in the flow solver. To handle the geometric complexity and moving boundary problems, overset grid scheme is incorporated with the solver that new connectivity data will be obtained at each time step. The Chimera overlapped grid scheme allows subdomains move relative to each other, and provides a great flexibility when the boundary movement creates large displacements. The performance of the two time integration schemes for time-accurate computations is investigated. For an unsteady flow which requires small physical time step, the pressure projection method was found to be computationally efficient since it does not require any subiterations procedure. It was observed that the artificial compressibility method requires a fast convergence scheme at each physical time step in order to satisfy incompressibility condition. This was obtained by using a GMRES- ILU(0) solver in our computations. When a line-relaxation scheme was used, the time accuracy was degraded and time-accurate computations became very expensive. The current geometry for the LOX boost turbopump has various rotating and stationary components, such as inducer, stators, kicker, hydrolic turbine, where the flow is extremely unsteady. Figure 1 shows the geometry and computed surface pressure of the inducer. The inducer and the hydrolic turbine rotate in different rotational speed. Author Computational Fluid Dynamics; Design Analysis; Grid Generation (Mathematics); Liquid Propellant Rocket Engines; Navier- Stokes Equation; Mathematical Models 20000064687 NASA Marshall Space Flight Center, Huntsville, AL USA Microgravity Isolation Control System Design Via High-Order Sliding Mode Control Shkolnikov, Ilya, Alabama Univ., USA; Shtessel, Yuri, Alabama Univ., USA; Whorton, Mark S., NASA Marshall Space Flight Center, USA; Jackson, Mark, NASA Marshall Space Flight Center, USA; [2000]; 11p; In English; American Control, 28-30 Jun. 2000, Chicago, IL, USA Contract(s)/Grant(s): RTOP 398-96-02; No Copyright; Avail: CASI; A03, Hardcopy; A01, Microfiche Vibration isolation control system design for a microgravity experiment mount is considered. The controller design based on dynamic sliding manifold (DSM) technique is proposed to attenuate the accelerations transmitted to an isolated experiment mount either from a vibrating base or directly generated by the experiment, as well as to stabilize the internal dynamics of this nonminimum phase plant. An auxiliary DSM is employed to maintain the high-order sliding mode on the primary sliding manifold in the presence of uncertain actuator dynamics of second order. The primary DSM is designed for the closed-loop system in sliding mode to be a filter with given characteristics with respect to the input external disturbances. Author Microgravity; Control Systems Design; Sliding; Vibration Isolators; Controllers 20000065643 Cornell Univ., Cornell Fracture Group, Ithaca, NY USA Simulating Fatigue Crack Growth in Spiral Bevel Gears Final Report Spievak, Lisa E., Cornell Univ., USA; Wawrzynek, Paul A., Cornell Univ., USA; Ingraffea, Anthony R., Cornell Univ., USA; May 2000; 126p; In English Contract(s)/Grant(s): NAG3-1993; RTOP 581-30-13; DA Proj. 1L1-62211-A-47-A Report No.(s): NASA/CR-2000-210062; E-12287; NAS 1.26:210062; ARL-CR-451; No Copyright; Avail: CASI; A07, Hardcopy; A02, Microfiche The majority of helicopter transmission systems utilize spiral bevel gears to convert the horizontal power from the engine into vertical power for the rotor. Due to the cyclical loading on a gear’s tooth, fatigue crack propagation can occur. In rotorcraft applications, a crack’s trajectory determines whether the gear failure will be benign or catastrophic for the aircraft. As a result, the capability to predict crack growth in gears is significant. A spiral bevel gear’s complex shape requires a three dimensional model of the geometry and cracks. The boundary element method in conjunction with linear elastic fracture mechanics theories is used to predict arbitrarily shaped three dimensional fatigue crack trajectories in a spiral bevel pinion under moving load conditions. The predictions are validated by comparison to experimental results. The sensitivity of the predictions to variations in loading conditions and crack growth rate model parameters is explored. Critical areas that must be understood in greater detail prior to predicting more accurate crack trajectories and crack growth rates in three dimensions are identified. Author Crack Propagation; Fatigue (Materials); Spiral Bevel Gears; Computerized Simulation; Mathematical Models; Rotary Wing Aircraft 93
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Scientific and Technical Aerospace
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Introduction Scientific and Technic
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Subject Divisions Table of Contents
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ground equipment and systems. For a
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Subject Categories of the Division
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48 Oceanography 139 Includes the ph
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72 Atomic and Molecular Physics 191
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Document Availability Information T
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Avail: NASA Public Document Rooms.
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NASA CASI Price Tables — Effectiv
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ALABAMA AUBURN UNIV. AT MONTGOMERY
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20000061433 Pisa Univ., Dipartiment
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English; 34th; 34th Thermophysics C
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ciency of the generated derivative
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20000063509 NASA Glenn Research Cen
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05 AIRCRAFT DESIGN, TESTING AND PER
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A long tradition of aerodynamic des
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sonic and transonic cases will be p
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20000061449 British Aerospace Publi
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20000064593 NASA Langley Research C
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performance required for a proposed
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ment cost and create better product
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tion (NPSS), is focused on the inte
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surface measurement techniques used
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with emphasis on the search for lin
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20000063520 NASA Kennedy Space Cent
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primary issues for it’s adaptatio
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Footage shows the night vertical ta
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necessary for ignition modeling, or
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Page 133 and 134: in Yellowstone National Park. We ar
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20000062717 Joint Inst. for Nuclear
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20000064015 Institute for Human Fac
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during 50% (SD 4%) of the breathing
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20000064711 Massachusetts Inst. of
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The analysis of this smaller data s
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vided a functional helmet mount. Th
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61 COMPUTER PROGRAMMING AND SOFTWAR
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The goal of multi-image classificat
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20000063526 Defence Science and Tec
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85 dB amplifier design evolved by o
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20000064594 New Mexico Univ., Elect
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20000064615 NASA Ames Research Cent
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declarations with a pattern recogni
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containing point where interpolatio
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has his own responsibility, while t
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the people, documents and projects
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and experimental technology, many o
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tems. In particular this applicatio
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Over the past decade, high performa
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expensive than a single analysis. I
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20000064726 Carnegie-Mellon Univ.,
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20000064099 Teledyne Brown Engineer
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20000066597 Geophysical Observatory
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20000065633 Institute TNO of Applie
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important conclusion is that for su
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est frame of the string. The modifi
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isotopes. The method and program we
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A detailed study is undertaken, usi
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20000063497 Kaiser Electro-Optics,
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delivers 60% of the x-ray flux from
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76 SOLID-STATE PHYSICS ��
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20000064660 Abdus Salam Internation
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20000067648 NASA Marshall Space Fli
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20000064703 Institute of Atomic Ene
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The BRST approach is applied to the
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20000067671 Hampton Univ., VA USA A
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82 DOCUMENTATION AND INFORMATION SC
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ecoming almost too cumbersome to be
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physical world. These are the two p
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with WFPC2 data. Tests of HSTphot
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A brief description is given of the
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gas, show variations that have rema
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egy, called Power In that would all
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A ABERRATION, 143, 198 ABRASION, 22
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COMPRESSIBLE FLOW, 83 COMPRESSION L
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FATIGUE (MATERIALS), 50, 93, 96 FAT
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LASING, 90 LATE STARS, 224 LATITUDE
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PATCH ANTENNAS, 74 PATHOLOGY, 98 PA
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SPACE PLATFORMS, 38 SPACE PROBES, 2
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WIND PROFILES, 137 WIND TUNNEL TEST
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Brown, Andy, 38 Brown, April S., 20
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Grosvenor, C. A., 70 Grosvenor, J.
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Lu, Gui-Ying, 50 Lugg, Desmond J.,
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Robertson, Tony, 39 Robinson, Jeffr
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Warner, J. D., 63 Warren, James, 16
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Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

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