NASA Scientific and Technical Aerospace Reports

20040111231 NASA Langley Research Center, Hampton, VA, USA
Aerodynamic Performance and Flow-Field Characteristics of Two Waverider-Derived Hypersonic Cruise Configurations
Cockrell, Charles E., Jr.; Huebner, Lawrence D.; Finley, Dennis B.; [1995]; 12 pp.; In English; Copyright; Avail: CASI; A03,
Hardcopy
The component integration of a class of hypersonic high-lift configurations known as waveriders into hypersonic cruise
vehicles was evaluated. A wind-tunnel model was developed which integrates realistic vehicle components with two waverider
shapes, referred to as the straight-wing and cranked-wing shapes. Both shapes were conical-flow-derived waveriders for a
design Mach number of 4.0. Experimental data and limited computational fluid dynamics (CFD) predictions were obtained
over a Mach number range of 1.6 to 4.63 at a Reynolds number of 2.0 x 10(exp 6) per foot. The CFD predictions and flow
visualization data confirmed the shock attachment characteristics of the baseline waverider shapes and illustrated the
waverider flow-field properties. Experimental data showed that no significant performance degradations, in terms of maximum
lift-to-drag ratios, occur at off-design Mach numbers for the waverider shapes and the integrated configurations. A comparison
of the fully-integrated waverider vehicles to the baseline shapes showed that the performance was significantly degraded when
all of the components were added to the waveriders, with the most significant degradation resulting from aftbody closure and
the addition of control surfaces. Both fully-integrated configurations were longitudinally unstable over the Mach number range
studied with the selected center of gravity location and for unpowered conditions. The cranked-wing configuration provided
better lateral-directional stability characteristics than the straight-wing configuration.
Author
Aerodynamic Configurations; Computational Fluid Dynamics; Flow Distribution; Hypersonic Vehicles; Waveriders; Wind
Tunnel Models; Aerodynamic Characteristics
20040111233 NASA Langley Research Center, Hampton, VA, USA
Velocity Fields of Axisymmetric Hydrogen-Air Counterflow Diffusion Flames from LDV, PIV, and Numerical
Computation
Pellett, Gerald L.; Wilson, Lloyd G.; Humphreys, William M., Jr.; Bartram, Scott M.; Gartrell, Luther R.; Isaac, K. M.; [1995];
24 pp.; In English; AIAA 31st Joint Propulsion Conference, 10-12 Jul. 1995, San Diego, CA, USA
Report No.(s): AIAA Paper 95-3112; Copyright; Avail: CASI; A03, Hardcopy
Laminar fuel-air counterflow diffusion flames (CFDFs) were studied using axisymmetric convergent-nozzle and
straight-tube opposed jet burners (OJBs). The subject diagnostics were used to probe a systematic set of H2/N2-air CFDFs
over wide ranges of fuel input (22 to 100% Ha), and input axial strain rate (130 to 1700 Us) just upstream of the airside edge,
for both plug-flow and parabolic input velocity profiles. Laser Doppler Velocimetry (LDV) was applied along the centerline
of seeded air flows from a convergent nozzle OJB (7.2 mm i.d.), and Particle Imaging Velocimetry (PIV) was applied on the
entire airside of both nozzle and tube OJBs (7 and 5 mm i.d.) to characterize global velocity structure. Data are compared to
numerical results from a one-dimensional (1-D) CFDF code based on a stream function solution for a potential flow input
boundary condition. Axial strain rate inputs at the airside edge of nozzle-OJB flows, using LDV and PIV, were consistent with
1-D impingement theory, and supported earlier diagnostic studies. The LDV results also characterized a heat-release hump.
Radial strain rates in the flame substantially exceeded 1-D numerical predictions. Whereas the 1-D model closely predicted
the max I min axial velocity ratio in the hot layer, it overpredicted its thickness. The results also support previously measured
effects of plug-flow and parabolic input strain rates on CFDF extinction limits. Finally, the submillimeter-scale LDV and PIV
diagnostics were tested under severe conditions, which reinforced their use with subcentimeter OJB tools to assess effects of
aerodynamic strain, and fueVair composition, on laminar CFDF properties, including extinction.
Author
Velocity Distribution; Hydrogen; Air Flow; Axial Strain; Counterflow; Diffusion Flames
20040111289 NASA Langley Research Center, Hampton, VA, USA
Numerical Simulations of Wake/Boundary Layer Interactions
Piomelli, Ugo; Choudhari, Meelan M.; Ovchinnikov, Victor; Balaras, Elias; [2003]; 13 pp.; In English; 41st Aerospace
Sciences Meeting and Exhibit, 6-9 Jan. 2003, Reno, NV, USA
Contract(s)/Grant(s): NAG1-2285
Report No.(s): AIAA Paper 2003-0975; Copyright; Avail: CASI; A03, Hardcopy
Direct and large-eddy simulations of the interaction between the wake of a circular cylinder and a flat-plate boundary layer
are conducted. Two Reynolds numbers are examined. The simulations indicate that at the lower Reynolds number the
boundary layer is buffeted by the unsteady Karman vortex street shed by the cylinder. The fluctuations, however, cannot be
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