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  • 11
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    Comparative performance tests on the Mod-2, 2.5-mW wind turbine with and without vortex generators (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A test program was conducted on the third Mod-2 unit at Goldendale, Washington, to systematically study the effect of vortex generators (VG's) on power performance. The subject unit was first tested without VG's to obtain baseline data. Vortex generators were then installed on the mid-blade assemblies, and the resulting 70% VG configuration was tested. Finally, vortex generators were mounted on the tip assemblies, and data was recorded for the 100% VG configuration. This test program and its results are discussed in this paper. The development of vortex generators is also presented.
    Keywords: AERODYNAMICS
    Type: DOE/NASA Workshop on Horizontal Axis Wind Turbine Technology; May 08, 1984 - May 10, 1984; Cleveland, OH; United States|DASCON Engineering, Collected Papers on Wind Turbine Technology; p 67-77
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 12
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    Comparative wind tunnel test at high Reynolds numbers of NACA 64 621 airfoils with two aileron configurations (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental program to measure the aerodynamic characteristics of the NACA 64-621 airfoil when equipped with plain ailerons of 0.38 chord and 0.30 chord and with 0.38 chord balanced aileron has been conducted in the pressurized O.S.U. 6 x 12 ft High Reynolds Number Wind Tunnel. Surface pressures were measured and integrated to yield lift and pressure drag coefficients for angles of attack from -3 to +42 deg and for selected aileron deflections from 0 to -90 deg at nominal Mach and Reynolds numbers of 0.25 and 5 x 10(exp 6). When resolved into thrust coefficient for wind turbine aerodynamic control applications, the data indicated the anticipated decrease in thrust coefficient with negative aileron deflection at low angles of attack; however, as angle of attack increased, thrust coefficients eventually became positive. All aileron configurations, even at -90 deg deflections showed this trend. Hinge moments for each configuration complete the data set.
    Keywords: AERODYNAMICS
    Type: DASCON Engineering, Collected Papers on Wind Turbine Technology; p 53-66|DOE/NASA Workshop on Horizontal Axis Wind Turbine Technology; May 08, 1984 - May 10, 1984; Cleveland, OH; United States
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  • 13
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    Comparative wind tunnel tests of NACA 23024 airfoils with several aileron and spoiler configurations (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper reviews research efforts at Wichita State University sponsored by NASA Lewis Research Center to design and evaluate aerodynamic braking devices which will be smaller and lighter than full-chord blade pitch control. Devices evaluated include a variety of aileron configurations, and spoilers located at both trailing edge and near the leading edge. The paper discusses analytical modeling, wind tunnel tests, and for some configurations, full-scale rotor tests. Current designs have not provided adequate control power at high angles of attack (low tip-speed-ratios). The reasons for these limitations are discussed. Analysis and wind tunnel test data indicate that several options are available to the designer to provide aerodynamic slowdown without full-chord pitch control. Three options are suggested; adding venting in front of the control surface hingeline, using spoilers located near the leading edge, and using a two-piece control combining downward deflection inboard with upward deflection outboard.
    Keywords: AERODYNAMICS
    Type: DASCON Engineering, Collected Papers on Wind Turbine Technology; p 47-52|DOE/NASA Workshop on Horizontal Axis Wind Turbine Technology; May 08, 1994 - May 10, 1994; Cleveland, OH; United States
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  • 14
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    Development of an upwind, finite-volume code with finite-rate chemistry (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Under this grant, two numerical algorithms were developed to predict the flow of viscous, hypersonic, chemically reacting gases over three-dimensional bodies. Both algorithms take advantage of the benefits of upwind differencing, total variation diminishing techniques and of a finite-volume framework, but obtain their solution in two separate manners. The first algorithm is a zonal, time-marching scheme, and is generally used to obtain solutions in the subsonic portions of the flow field. The second algorithm is a much less expensive, space-marching scheme and can be used for the computation of the larger, supersonic portion of the flow field. Both codes compute their interface fluxes with a temporal Riemann solver and the resulting schemes are made fully implicit including the chemical source terms and boundary conditions. Strong coupling is used between the fluid dynamic, chemical and turbulence equations. These codes have been validated on numerous hypersonic test cases and have provided excellent comparison with existing data. This report summarizes the research that took place from August 1,1994 to January 1, 1995.
    Keywords: AERODYNAMICS
    Type: NASA-CR-197747 , NAS 1.26:197747 , MCAT-95-01
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  • 15
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    CFD research, parallel computation and aerodynamic optimization (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Over five years of research in Computational Fluid Dynamics and its applications are covered in this report. Using CFD as an established tool, aerodynamic optimization on parallel architectures is explored. The objective of this work is to provide better tools to vehicle designers. Submarine design requires accurate force and moment calculations in flow with thick boundary layers and large separated vortices. Low noise production is critical, so flow into the propulsor region must be predicted accurately. The High Speed Civil Transport (HSCT) has been the subject of recent work. This vehicle is to be a passenger vehicle with the capability of cutting overseas flight times by more than half. A successful design must surpass the performance of comparable planes. Fuel economy, other operational costs, environmental impact, and range must all be improved substantially. For all these reasons, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer and other disciplines.
    Keywords: AERODYNAMICS
    Type: NASA-CR-197748 , NAS 1.26:197748 , MCAT-95-18
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  • 16
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    A combined geometric approach for solving the Navier-Stokes equations on dynamic grids (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A combined geometric approach for solving the Navier-Stokes equations is presented for the analysis of planar, unsteady flow about mechanisms with components in moderate relative motion. The approach emphasizes the relationships between the geometry model, grid, and flow model for the benefit of the total dynamics problem. One application is the analysis of the restart operation of a variable-geometry, high-speed inlet.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106919 , E-9630 , NAS 1.15:106919 , Conference on Numerical Methods for Fluid Dynamics; Apr 03, 1995 - Apr 06, 1995; Oxford; Guinea
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  • 17
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    Active control of panel vibrations induced by a boundary layer flow (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to consider the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. Although the sound radiation has not been included, the vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings are presented in three sections. In section two we describe results on the boundary control of nonlinear panel vibration, with or without flow excitation. Sections three and four are concerned with some analytical and numerical results in the optimal control of the linear and nonlinear panel vibrations, respectively, excited by the flow pressure fluctuations. Finally, in section five, we draw some conclusions from research findings.
    Keywords: AERODYNAMICS
    Type: NASA-CR-197867 , NAS 1.26:197867
    Format: application/pdf
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  • 18
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    Semi-span model testing in the National Transonic Facility (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The objectives of the present research are: (1) to develop a computational approach to support semi-span model test techniques in the NTF; and (2) to integrate this approach with the conduct of an experimental test program. To meet these objectives, the following approach is taken. A state-of-the-art three-dimensional Navier-Stokes solver is employed to compute the flow over both a full-span configuration and a semi-span configuration mounted on the sidewall of the tunnel. The computations are validated by making direct comparisons to experimental data for both configurations. Then, the semi-span computational results are compared to the full-span results to document how the flow over the semi-span configuration differs from that over the full-span configuration. The results of this comparative study will be used to provide a conceptual framework within which a semi-spa model test technique may be implemented in the NTF.
    Keywords: AERODYNAMICS
    Type: NASA-CR-199272 , NAS 1.26:199272
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  • 19
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    Navier-Stokes calculations of rotor-airframe interaction in forward flight (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A method for analyzing the mutual aerodynamic interaction between a rotor and an airframe model has been developed. This technique models the rotor implicitly through the source terms of the momentum equations. A three-dimensional, incompressible, laminar, Navier-Stokes solver in cylindrical coordinates was developed for analyzing the rotor-airframe problem. The calculations are performed on a simplified rotor-airframe model at an advance ratio of 0.1. The airframe surface pressure predictions are found to be in good agreement with wind tunnel test data. Results are also presented for velocity and pressure field distributions in the wake of the rotor.
    Keywords: AERODYNAMICS
    Type: American Helicopter Society, Journal (ISSN 0002-8711); 40; 2; p. 57-67
    Format: text
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  • 20
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    An assessment of viscous effects in computational simulation of benign and burst vortex flows on generic fighter wind-tunnel models using TEAM code (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Vortex flows on a twin-tail and a single-tail modular transonic vortex interaction (MTVI) model, representative of a generic fighter configuration, are computationally simulated in this study using the Three-dimensional Euler/Navier-Stokes Aerodynamic Method (TEAM). The primary objective is to provide an assessment of viscous effects on benign (10 deg angle of attack) and burst (35 deg angle of attack) vortex flow solutions. This study was conducted in support of a NASA project aimed at assessing the viability of using Euler technology to predict aerodynamic characteristics of aircraft configurations at moderate-to-high angles of attack in a preliminary design environment. The TEAM code solves the Euler and Reynolds-average Navier-Stokes equations on patched multiblock structured grids. Its algorithm is based on a cell-centered finite-volume formulation with multistage time-stepping scheme. Viscous effects are assessed by comparing the computed inviscid and viscous solutions with each other and experimental data. Also, results of Euler solution sensitivity to grid density and numerical dissipation are presented for the twin-tail model. The results show that proper accounting of viscous effects is necessary for detailed design and optimization but Euler solutions can provide meaningful guidelines for preliminary design of flight vehicles which exhibit vortex flows in parts of their flight envelope.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4650 , NAS 1.26:4650
    Format: application/pdf
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