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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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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Computational design of low aspect ratio wing-winglets for transonic wind-tunnel testing

A computational design has been performed for three different low aspect ratio wing planforms fitted with nonplanar winglets; one of the three planforms has been selected to be constructed as a wind tunnel model for testing in the NASA LaRC 7 x 10 High Speed Wind Tunnel. A design point of M = 0.8, CL approx = 0.3 was selected, for wings of aspect ratio equal to 2.2, and leading edge sweep angles of 45 and 50 deg. Winglet length is 15 percent of the wing semispan, with a cant angle of 15 deg, and a leading edge sweep of 50 deg. Winglet total area equals 2.25 percent of the wing reference area. This report summarizes the design process and the predicted transonic performance for each configuration.

Kuhlman, John M.↗
NASA NTRS1989

Computational design of low aspect ratio wing-winglet configurations for transonic wind-tunnel tests

Computational designs were performed for three different low aspect ratio wing planforms fitted with nonplanar winglets; one of the three configurations was selected to be constructed as a wind tunnel model for testing in the NASA LaRC 8-foot transonic pressure tunnel. A design point of M = 0.8, C(sub L) is approximate or = to 0.3 was selected, for wings of aspect ratio equal to 2.2, and leading edge sweep angles of 45 deg and 50 deg. Winglet length is 15 percent of the wing semispan, with a cant angle of 15 deg, and a leading edge sweep of 50 deg. Winglet total area equals 2.25 percent of the wing reference area. The design process and the predicted transonic performance are summarized for each configuration. In addition, a companion low-speed design study was conducted, using one of the transonic design wing-winglet planforms but with different camber and thickness distributions. A low-speed wind tunnel model was constructed to match this low-speed design geometry, and force coefficient data were obtained for the model at speeds of 100 to 150 ft/sec. Measured drag coefficient reductions were of the same order of magnitude as those predicted by numerical subsonic performance predictions.

Kuhlman, John M.↗
NASA NTRS1988

Computational design of low aspect ratio wing-winglet configurations for transonic wind-tunnel tests

A computational design has been performed for three different low aspect ratio wing planforms fitted with nonplanar winglets; one of the three planforms has been selected to be constructed as a wind tunnel model for testing in the NASA LaRC 7 x 10 High Speed Wind Tunnel. A design point of M = 0.8, CL approx = 0.3 was selected, for wings of aspect ratio equal to 2.2, and leading edge sweep angles of 45 and 50 deg. Winglet length is 15 percent of the wing semispan, with a cant angle of 15 deg, and a leading edge sweep of 50 deg. Winglet total area equals 2.25 percent of the wing reference area. This report summarizes the design process and the predicted transonic performance for each configuration.

Kuhlman, John M.↗
NASA NTRS2011

Capability Extension to the Turbine Off-Design Computer Program AXOD With Applications to the Highly Loaded Fan-Drive Turbines

The axial flow turbine off-design computer program AXOD has been upgraded to include the outlet guide vane (OGV) into its acceptable turbine configurations. The mathematical bases and the techniques used for the code implementation are described and discussed in lengths in this paper. This extended capability is verified and validated with two cases of highly loaded fan-drive turbines, designed and tested in the V/STOL Program of NASA. The first case is a 4 1/2-stage turbine with an average stage loading factor of 4.66, designed by Pratt & Whitney Aircraft. The second case is a 3 1/2-stage turbine with an average loading factor of 4.0, designed in-house by the NASA Lewis Research Center (now the NASA Glenn Research Center). Both cases were experimentally tested in the turbine facility located at the Glenn Research Center. The processes conducted in these studies are described in detail in this paper, and the results in comparison with the experimental data are presented and discussed. The comparisons between the AXOD results and the experimental data are in excellent agreement.

Chen, Shu-cheng S.↗
NASA NTRS1981

Performance of computer-designed small-sized four-stage depressed collector for operation of dual-mode traveling wave tube

A computer-designed axisymmetric 2.4-cm-diameter four-stage depressed collectors was evaluated in conjunction with an octave bandwidth, dual-mode traveling wave tube (TWT). The TWT was operated over a wide range of conditions to simulate different applications. The collector performance was optimized (within the constraint of fixed collector geometry which was designed for operation of the TWT at saturation) over the range of TWT operating conditons covered. For operation of the dual-mode TWT at saturation, average collector efficiencies of 81 1/2 and 82 percent for the high and low modes, respectively, were obtained across an octave bandwidth, leading to a three-fold increase in the TWT overall efficiency. For operation of the TWT in the linear, low distortion range, collector efficiencies of 87 to 92 percent were obtained, leading to TWT overall efficiencies as high as 35 percent. For operation of the dual-mode TWT over a 10 to 1 range in output power, overall efficiencies of 14 to 41 percent were obtained.

Ramins, P.↗
NASA NTRS2002

Effect of Random Geometric Uncertainty on the Computational Design of a 3-D Flexible Wing

The effect of geometric uncertainty due to statistically independent, random, normally distributed shape parameters is demonstrated in the computational design of a 3-D flexible wing. A first-order second-moment statistical approximation method is used to propagate the assumed input uncertainty through coupled Euler CFD aerodynamic / finite element structural codes for both analysis and sensitivity analysis. First-order sensitivity derivatives obtained by automatic differentiation are used in the input uncertainty propagation. These propagated uncertainties are then used to perform a robust design of a simple 3-D flexible wing at supercritical flow conditions. The effect of the random input uncertainties is shown by comparison with conventional deterministic design results. Sample results are shown for wing planform, airfoil section, and structural sizing variables.

Gumbert, C. R.↗
NASA NTRS1965

Guidance computer design

Some 22 years have elapsed since the first digital computer was completed. For the past several years, digital guidance computers have flown in airplanes, missiles, and rockets. Some of these vehicles are scarcely bigger than an early computer, whose performance is surpassed by the guidance computers they carry.

APOLLO SPACECRAFT↗
NASA NTRS1994

Modeling Improvements and Users Manual for Axial-flow Turbine Off-design Computer Code AXOD

An axial-flow turbine off-design performance computer code used for preliminary studies of gas turbine systems was modified and calibrated based on the experimental performance of large aircraft-type turbines. The flow- and loss-model modifications and calibrations are presented in this report. Comparisons are made between computed performances and experimental data for seven turbines over wide ranges of speed and pressure ratio. This report also serves as the users manual for the revised code, which is named AXOD.

Glassman, Arthur J.↗
NASA NTRS1976

Computer-aided design and computer science technology

A description is presented of computer-aided design requirements and the resulting computer science advances needed to support aerospace design. The aerospace design environment is examined, taking into account problems of data handling and aspects of computer hardware and software. The interactive terminal is normally the primary interface between the computer system and the engineering designer. Attention is given to user aids, interactive design, interactive computations, the characteristics of design information, data management requirements, hardware advancements, and computer science developments.

Fulton, R. E.↗
NASA NTRS1976

A systematic method for computer design of supercritical airfoils in cascade

A computer code has been developed for the direct calculation of shockless transonic airfoils whose pressure distributions can be assigned within reasonable limits. The partial differential equations of two-dimensional inviscid gas dynamics are solved by analytic continuation into the domain of two independent complex characteristic coordinates. The domain of integration is mapped conformally onto the unit circle in the hodograph plane of one of these coordinates. It is possible to formulate a boundary value problem on this circle for the stream function that is well posed in the case of transonic flow. This enables the formulation of a procedure for the calculation of an airfoil on which the speed is prescribed as a function of the arc length

Garabedian, P.↗
NASA NTRS1996

Cassini Science Operations and Planning Computer Design

The Cassini Science Operations and Planning Computers (SOPC) are meant to give Cassini investigators and the Huygens Probe Operations Centre (HPOC) more directed control of and responsibility for their instruments and their data and to reduce mission operations cost.SOPCs give the investigators the ability to command their instrument directly, but also the responsibility to do so correctly.

Cassini↗
NASA NTRS1989

Computational design aspects of a NASP nozzle/afterbody experiment

This paper highlights the influence of computational methods on design of a wind tunnel experiment which generically models the nozzle/afterbody flow field of the proposed National Aerospace Plane. The rectangular slot nozzle plume flow field is computed using a three-dimensional, upwind, implicit Navier-Stokes solver. Freestream Mach numbers of 5.3, 7.3, and 10 are investigated. Two-dimensional parametric studies of various Mach numbers, pressure ratios, and ramp angles are used to help determine model loads and afterbody ramp angle and length. It was found that the center of pressure on the ramp occurs at nearly the same location for all ramp angles and test conditions computed. Also, to prevent air liquefaction, it is suggested that a helium-air mixture be used as the jet gas for the highest Mach number test case.

Ruffin, Stephen M.↗
NASA NTRS1995

Off-design computer code for calculating the aerodynamic performance of axial-flow fans and compressors

An off-design axial-flow compressor code is presented and is available from COSMIC for predicting the aerodynamic performance maps of fans and compressors. Steady axisymmetric flow is assumed and the aerodynamic solution reduces to solving the two-dimensional flow field in the meridional plane. A streamline curvature method is used for calculating this flow-field outside the blade rows. This code allows for bleed flows and the first five stators can be reset for each rotational speed, capabilities which are necessary for large multistage compressors. The accuracy of the off-design performance predictions depend upon the validity of the flow loss and deviation correlation models. These empirical correlations for the flow loss and deviation are used to model the real flow effects and the off-design code will compute through small reverse flow regions. The input to this off-design code is fully described and a user's example case for a two-stage fan is included with complete input and output data sets. Also, a comparison of the off-design code predictions with experimental data is included which generally shows good agreement.

Schmidt, James F.↗
NASA NTRS1986

Verification of an improved computational design procedure for TWT-dynamic refocuser-MDC systems with secondary electron emission losses

A computational procedure for the design of TWT-refocuser-MDC systems was used to design a short 'dynamic' refocusing system and highly efficient four-stage depressed collector for a 200-W 8-18-GHz TWT. The computations were carried out with advanced multidimensional computer programs which model the electron beam as a series of disks of charge and follow their trajectories from the RF input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semiquantitatively by injecting a representative beam of secondary electrons into the MDC analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particular form of isotropic graphite that was selected for its low secondary electron yield, thermal expansion characteristics, ease of machinability and vacuum properties. This MDC was tested at CW for more than 1000 h with negligible degradation in TWT and MDC performances.

Ramins, P.↗
NASA NTRS1971

The STAR /self-testing and repairing/ computer - An investigation of the theory and practice of fault-tolerant computer design.

This paper presents the results obtained in a continuing investigation of fault-tolerant computing which is being conducted at the Jet Propulsion Laboratory. Initial studies led to the decision to design and construct an experimental computer with dynamic (standby) redundancy, including replaceable subsystems and a program rollback provision to eliminate transient errors. This system, called the STAR computer, began operation in 1969. The following aspects of the STAR system are described: architecture, reliability analysis, software, automatic maintenance of peripheral systems, and adaptation to serve as the central computer of an outer-planet exploration spacecraft.

A Avizienis↗