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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The effects of streamline curvature and swirl on turbulent flows in curved ducts

A technique for improving the numerical predictions of turbulent flows with the effect of streamline curvature is developed. Separated flows, the flow in a curved duct, and swirling flows are examples of flow fields where streamline curvature plays a dominant role. A comprehensive literature review on the effect of streamline curvature was conducted. New algebraic formulations for the eddy viscosity incorporating the kappa-epsilon turbulence model are proposed to account for various effects of streamline curvature. The loci of flow reversal of the separated flows over various backward-facing steps are employed to test the capability of the proposed turbulence model in capturing the effect of local curvature. The inclusion of the effect of longitudinal curvature in the proposed turbulence model is validated by predicting the distributions of the static pressure coefficients in an S-bend duct and in 180 degree turn-around ducts. The proposed turbulence model embedded with transverse curvature modification is substantiated by predicting the decay of the axial velocities in the confined swirling flows. The numerical predictions of different curvature effects by the proposed turbulence models are also reported.

Cheng, Chih-Hsiung↗
NASA NTRS1990

Unsteady blade pressure measurements for the SR-7A propeller at cruise conditions

The unsteady blade surface pressures were measured on the SR-7A propeller. The freestream Mach no., inflow angle, and advance ratio were varied while measurements were made at nine blade stations. At a freestream Mach no. of 0.8, the data in terms of unsteady pressure coefficient vs. azimuth angle are compared to an unsteady 3-D Euler solution, yielding very encouraging results. The code predicts the shape (phase) of the waveform very well, while the magnitude is over-predicted in many cases. At tunnel Mach nos. below 0.6, an unusually large response on the suction surface at 0.15 chord and 0.88 radius was observed. The behavior of this response suggests the presence of a leading edge vortex. The midchord measuring stations on the suction surface exhibit a response that leads the forcing function while most other locations show a phase lag.

Heidelberg, L. J.↗
NASA NTRS1991

The NASA aircraft noise prediction program improved propeller analysis system

The improvements and the modifications of the NASA Aircraft Noise Prediction Program (ANOPP) and the Propeller Analysis System (PAS) are described. Comparisons of the predictions and the test data are included in the case studies for the flat plate model in the Boundary Layer Module, for the effects of applying compressibility corrections to the lift and pressure coefficients, for the use of different weight factors in the Propeller Performance Module, for the use of the improved retarded time equation solution, and for the effect of the number grids in the Transonic Propeller Noise Module. The DNW tunnel test data of a propeller at different angles of attack and the Dowty Rotol data are compared with ANOPP predictions. The effect of the number of grids on the Transonic Propeller Noise Module predictions and the comparison of ANOPP TPN and DFP-ATP codes are studied. In addition to the above impact studies, the transonic propeller noise predictions for the SR-7, the UDF front rotor, and the support of the enroute noise test program are included.

Nguyen, L. Cathy↗
NASA NTRS1990

Sensitivity of high-accuracy Tracking and Data Relay Satellite System (TDRSS) user spacecraft orbit determination to tracking schedules

The results of a study to analyze the dependence of TDRSS user spacecraft orbit determination consistencies on varying tracking schedules are presented. In this study, the TDRS-East orbit determination results obtained utilizing Bilateration Ranging Transponder System data were evaluated. Six state parameters, three position and three velocity components and the solar radiation pressure coefficient, are estimated for TDRS-East. It is concluded that, in order to achieve high-precision orbit determination, the tracking coverage should not fall below 10 minutes every two orbits as decreasing it to every four orbits will significantly degrade the accuracy; present state-of-the-art consistency in orbit determination using TDRSS tracking is approximately 15 to 20 meters.

Doll, C. E.↗
NASA NTRS1990

Unsteady blade pressure measurements for the SR-7A propeller at cruise conditions

The unsteady blade surface pressures were measured on the SR-7A propeller. The freestream Mach number, inflow angle, and advance ratio were varied while measurements were made at nine blade stations. At a freestream Mach number of 0.8, the data in terms of unsteady pressure coefficient versus azimuth angle are compared to an unsteady three-dimensional Euler solution, yielding very encouraging results. The code predicts the shape (phase) of the waveform very well, while the magnitude is over-predicted in many cases. At tunnel Mach numbers below 0.6, an unusually large response on the suction surface at 0.15 chord and 0.88 radius was observed. The behavior of this response suggests the presence of a leading-edge vortex.

Heidelberg, L. J.↗
NASA NTRS1991

An efficient hybrid scheme for the analysis of counter rotating propellers

An efficient solution procedure has been developed for analyzing inviscid unsteady flow past counter rotating propellers. This scheme is first order accurate in time and second order in space, and has been extended to fourth order accuracy in the axial direction. The solution procedure has been applied to a 2-bladed SR-7 single rotation propeller and to a GE F7/A7 counter rotation propeller. The pressure coefficients and the global quantities, power and thrust, show good comparison with experimental measurements.

Srivastava, R.↗
NASA NTRS1991

Navier-Stokes simulation of a close-coupled canard-wing-body configuration

The thin-layer Navier-Stokes equations are solved for the flow about a coplanar close-coupled canard-wing-body configuration at a transonic Mach number of 0.90 and at angles of attack ranging from 0 to 12 degrees. The influence of the canard on the wing flowfield, including canard-wing vortex interaction and wing vortex breakdown, is investigated. A study of canard downwash and canard leading-edge vortex effects, which are the primary mechanisms of the canard-wing interaction, is emphasized. Comparisons between the computations and experimental measurements of surface pressure coefficients, lift, drag and pitching moment data are favorable. A grid refinement study for configurations with and without canard shows that accurate results are obtained using a refined grid for angles of attack where vortex burst is present. At an angle of attack of approximately 12 deg, favorable canard-wing interaction which delays wing vortex breakdown is indicated by the computations and is in good agreement with experimental findings.

Tu, Eugene L.↗
NASA NTRS1989

Transonic viscous flow computations about a complete aircraft using the Navier-Stokes equations

A numerical approach for simulating the viscous transonic flow about the complete F-16A fighter aircraft is presented using the Navier-Stokes equations. This finite difference approach utilizes a body conforming zonal grid system to provide appropriate viscous clustering near all body surfaces. A comparison between computational and experimental pressure coefficients is good, and integrated quantities such as lift and drag are within 2.6 percent and 1.6 percent, respectively. The versatility of the method is demonstrated by further modeling the flow inside the inlet up to the compressor face and the exhaust nozzle plume. Results for the F-16A in sideslip are also presented and indicate the proper trends.

Chaderjian, Neal M.↗
NASA NTRS1991

Computational flow predictions for hypersonic drag devices

The effectiveness of two types of hypersonic decelerators are computationally examined: mechanically deployable flares and inflatable ballutes. CFD is used to predict the flowfield around a solid rocket motor (SRM) with a deployed decelerator. The computations are performed with an ideal gas solver using an effective specific heat ratio of 1.15. The surface pressure coefficients, the drag, and the extent of the compression corner separation zone predicted by the ideal gas solver compare well with those predicted by the nonequilibrium solver. The ideal gas solver is computationally inexpensive and is shown to be well suited for preliminary design studies. The computed solutions are used to determine the size and shape of the decelerator that are required to achieve a drag coefficient of 5 in order to assure that the SRM will splash down in the Pacific Ocean. Heat transfer rates to the SRM and the decelerators are predicted to estimate the amount of thermal protection required.

Tokarcik, Susan↗
NASA NTRS1991

Results of the space shuttle vehicle ascent air data system probe calibration test using a 0.07-scale external tank forebody model (68T) in the AEDC 16-foot transonic wind tunnel (IA-310), volume 1

A recalibration of the Space Shuttle Vehicle Ascent Air Data System probe was conducted in the Arnold Engineering Development Center (AEDC) transonic wind tunnel. The purpose was to improve on the accuracy of the previous calibration in order to reduce the existing uncertainties in the system. A probe tip attached to a 0.07-scale External Tank Forebody model was tested at angles of attack of -8 to +4 degrees and sideslip angles of -4 to +4 degrees. High precision instrumentation was used to acquire pressure data at discrete Mach numbers ranging from 0.6 to 1.55. Pressure coefficient uncertainties were estimated at less than 0.0020. Data is given in graphical and tabular form.

Collette, J. G. R.↗
NASA NTRS1991

Results of the space shuttle vehicle ascent air data system probe calibration test using a 0.07-scale external tank forebody model (68T) in the AEDC 16-foot transonic wind tunnel (IA-310), volume 2

A recalibration of the Space Shuttle Vehicle Ascent Air Data System probe was conducted in the Arnold Engineering and Development Center (AEDC) transonic wind tunnel. The purpose was to improve on the accuracy of the previous calibration in order to reduce the existing uncertainties in the system. A probe tip attached to a 0.07-scale External Tank Forebody model was tested at angles of attack of -8 to +4 degrees and sideslip angles of -4 to +4 degrees. High precision instrumentation was used to acquire pressure data at discrete Mach numbers ranging from 0.6 to 1.55. Pressure coefficient uncertainties were estimated at less than 0.0020. Additional information is given in tabular form.

Collette, J. G. R.↗
NASA NTRS1992

Experimental study of a generic high-speed civil transport: Tabulated data

An experimental study of a generic high-speed civil transport was conducted in LaRC's 8-Foot Transonic Pressure Tunnel. The data base was obtained for the purpose of assessing the accuracy of various levels of computational analysis. Two models differing only in wing tip geometry were tested with and without flow-through nacelles. The baseline model has a curved or crescent wing tip shape while the second model has a more conventional straight wing tip shape. The study was conducted at Mach numbers from 0.30-1.19. Force data were obtained on both the straight and curved wing tip models. Only the curved wing tip model was instrumented for measuring pressures. Longitudinal and lateral-directional aerodynamic data are presented without analysis in tabulated form. Pressure coefficients for the curved wing tip model are also presented in tabulated form.

Belton, Pamela S.↗
NASA NTRS1992

Data reduction formulas for the 16-foot transonic tunnel: NASA Langley Research Center, revision 2

The equations used by the 16-Foot Transonic Wind Tunnel in the data reduction programs are presented in nine modules. Each module consists of equations necessary to achieve a specific purpose. These modules are categorized in the following groups: (1) tunnel parameters; (2) jet exhaust measurements; (3) skin friction drag; (4) balance loads and model attitudes calculations; (5) internal drag (or exit-flow distribution); (6) pressure coefficients and integrated forces; (7) thrust removal options; (8) turboprop options; and (9) inlet distortion.

Mercer, Charles E.↗
NASA NTRS1992

Wall interference calculation in a transonic test section including simulation of discrete slots

A computational simulation of a transonic wind tunnel test section with longitudinally slotted walls is described. This nonlinear slot model includes dynamic-pressure effects and a plenum pressure constraint. The simulation method developed is found to be a useful tool for analyzing the nature of the flowfield that exists in a longitudinally slotted transonic test section. Results obtained from the discrete-slot model are similar to those of a homogeneous model when a plenum pressure coefficient of zero is utilized, indicating little effect of slot discreteness with the transport aircraft models examined.

Al-Saadi, Jassim A.↗
NASA NTRS1992

Efficient simulation of incompressible viscous flow over single and multi-element airfoils

Incompressible viscous turbulent flows over single- and multiple-element airfoils are numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The solution algorithm uses the method of pseudocompressibility with an upwind-differencing scheme for the convective fluxes and an implicit line-relaxation scheme to study high-lift take-off and landing configurations and to compute lift and drag at various angles of attack up to stall. Two different turbulence models are tested in computing the flow over an NACA 4412 airfoil. The approach used for multiple-element airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared: a patched system of grids and an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Excellent agreement with experimental surface-pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of one minute of CPU time on a CRAY YMP per element in the airfoil configuration.

Rogers, Stuart E.↗
NASA NTRS1992

A summary of the computational fluid dynamics analysis of the hypersonic flights of Pegasus

A computational fluid dynamics (CFD) analysis of the hypersonic flights of the NASA's Pegasus launch vehicle was carried out using the PARC code. The flight data included heat transfer rates and sparse pressure coefficients primarily in the fillet region of the vehicle. Since the CFD simulations did not account for ablation at the vehicle surface, the test heat transfer results were obtained for the low Mach number simulations; as the Mach number was increased, the ablative effects at the vehicle surface became more apparent and contributed to the error.

Fricker, Darren↗
NASA NTRS1984

Ames 40 X 80/80 X 120 Foot Wind Tunnel: Turning Vanes Design

A number of different turning vanes are designed for the NASA Ames wind tunnel. Computer codes are used to design and analyze the turning vanes to insure that they comply with their individual constraints. The presentation is given in viewgraph format and displays pressure coefficients for the different turning vanes as well as loss coefficients versus inlet flow angles.

Sanz, J.↗
NASA NTRS1993

SUMS experiment flight results on STS-35

Calibrated pressure measurements for species with mass to charge ratios up to 50 amu/e(-) were obtained from the Shuttle Upper Atmosphere Mass Spectrometer (SUMS) experiment during reentry on the STS-35 mission. Data were collected from 180 km, when the signal rose above the background, to about 87 km, when the SUMS system automatically closed the gas inlet value. However, data above 115 km was contaminated from a source of gas emanating from pressure transducers connected in parallel to the mass spectrometer. At lower altitudes, the pressure transducer data is compared with the mass spectrometer total pressure with excellent agreement. The free-stream density in the rarefied flow flight regime is calculated using an orifice pressure coefficient model based upon direct simulation Monte Carlo results. This density, when compared with the 1976 U.S. standard atmosphere model, exhibits the wave-like nature seen on previous flights using accelerometry. In addition, selected spectra are presented at higher altitudes (320 km) showing the effects of the ingestion of gases from a forward fuselage fuel dump. An analysis of the spectra data from this event is presented to show that no significant permanent changes occurred which affected the data interpretation at lower altitudes. Further, the localized chemistry from the individual species during the onset of aerodynamic heating is examined to the extent possible for a closed source system, such as SUMS. Near the orifice entrance, a significant amount of CO2 was generated from chemical reactions with the carbon panels of the Orbiter and absorbed oxygen on the system tubing.

Blanchard, Robert C.↗