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  • 1
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    Progress toward synergistic hypermixing nozzles (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Mean flow measurements have been obtained for air-to-air mixing downstream of swept and unswept ramp wall-mounted hypermixing nozzle configurations. Aside from the sweep of the ramps, the two nozzle configurations investigated are identical. The nozzles inject three parallel supersonic jets at a 15-deg angle (relative to the wind tunnel wall) into a supersonic freestream. Mach number and volume fraction distributions in a transverse plane 11.1 nozzle heights downstream from the nozzle exit plane were measured. Data are presented for a freestream Mach number of three at a matched static pressure condition and also at an underexpanded static pressure condition (pressure ratio equal to 5). Surface oil flow visualization was used to investigate the near-wall flow behavior. The results indicate that the swept ramp injectors produce stronger and larger vortex pairs than the unswept ramp injectors. The increased interaction between the swept ramp model's larger vortex pairs yields better mixing characteristics for this model.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-2264
    Format: text
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  • 2
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    Experimental investigation of turbulent flow through a circular-to-rectangular transition duct (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An incompressible, turbulent, swirl-free flow through a circular-to-rectangular transition duct was studied experimentally. The cross-sectional geometry all along the duct was defined using the equation of a superellipse. The three mean velocity components and the six Reynolds stress components were measured at two axial stations downstream from the transition. It is shown that a secondary flow vortex pair which develops along the duct sidewalls significantly distorts the mean and turbulence fields. At the duct exit, the flow is not in local equilibrium, but recovers to local equilibrium conditions in the rectangular extension duct. Analysis demonstrates that conventional wall functions are not applicable at all streamwise locations in the duct.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-1505
    Format: text
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  • 3
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    Surface and flow field measurements in a symmetric crossing shock wave/turbulent boundary layer flow (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of an experimental investigation of a symmetric crossing shock/turbulent boundary layer interaction are presented for a Mach number of 3.44 and deflections angles of 2, 6, 8 and 9 deg. The interaction strengths vary from weak to strong enough to cause a large region of separated flow. Measured quantities include surface static pressure and flowfield Pitot pressures. Pitot profiles in the plane of symmetry through the interaction region are shown for various deflection angles. Oil flow visualization and the results of a trace gas streamline tracking technique are also presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2634
    Format: text
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  • 4
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    Experimental investigation of a single flush-mounted hypermixing nozzle (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Reported herein are the results of an experimental wind tunnel investigation of a circular supersonic jet (Mj = 3.47) injected at a 10 degree angle into a supersonic freestream. Measurements were made for nominal freestream Mach numbers of 1.6, 2.0, 2.5 and 3.0. Three jet total pressures were run at each freestream Mach number, resulting in twelve separate operating conditions. The measurements indicate the presence of two pairs of contra-rotating vortices. One pair follows the jet trajectory and tends to split the jet into two streams. A smaller pair, rotating in an opposite sense, develops in the near wall region. Reported results include Mach number and volume fraction distributions in the cross plane, as well as jet penetration and mixing efficiency.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 90-5240
    Format: text
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  • 5
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    Evaluation of a technique to generate artificially thickened boundary layers in supersonic and hypersonic flows (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of using a contoured honeycomb model to generate a thick boundary layer in high-speed, compressible flow was investigated. The contour of the honeycomb was tailored to selectively remove momentum in a minimum of streamwise distance to create an artificially thickened turbulent boundary layer. Three wind tunnel experiments were conducted to verify the concept. Results indicate that this technique is a viable concept, especially for high-speed inlet testing applications. In addition, the compactness of the honeycomb boundary layer simulator allows relatively easy integration into existing wind tunnel model hardware.
    Keywords: AERODYNAMICS
    Type: NASA-TP-3142 , E-5660 , NAS 1.60:3142
    Format: application/pdf
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  • 6
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    Experimental and numerical investigation of supersonic flow through a square duct (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Steady, developing, adiabatic supersonic flow in a square duct is investigated for an inlet Mach number of 3.91 and a unit Reynolds number of 1.8 x 10 to the 6th/m. The numerical results for laminar flow show that two secondary flow cells develop in the near vicinity of the corner which are centered about the corner bisector and distort the primary flow in this region. For turbulent flow, the experimental results indicate that two secondary flow cells also develop about the corner bisector, but are directed in an opposite sense to that observed for the laminar case. Numerical results based on the Baldwin-Lomax model show that this model is incapable of predicting turbulence-generated secondary flow cells. For a suitable choice of constants, the Gessner-Emery model is able to predict the strength of these cells, but is deficient with respect to predicting their positions in the flow and their distorting influence on the primary flow. These observations are based on comparisons made in this paper between predicted and measured total pressure contours, cross flow velocity profiles, and local wall shear stress distributions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-1622
    Format: text
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  • 7
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    Further experiments on supersonic turbulent flow development in a square duct (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The mean-flow structure of supersonic, turbulent, adiabatic-wall flow in a square duct is investigated experimentally over a development length x/D = 0-50 for a uniform flow, Mach 3.9 condition at the duct inlet. The results show that a secondary flow cell structure develops which is similar to that for the incompressible case. Development of the primary flow is influenced by the combined effects of the secondary flow and the streamwise adverse pressure gradient. Total pressure, axial mean velocity, and Mach number profiles are presented which show that the outer flow is sensitive primarily to the streamwise pressure gradient, while flow in the near-wall region is dominated by the secondary flow. Axial mean-velocity profiles plotted in terms of van Driest-scaled variables show that a well-defined log-law region exists in the near-wall layer. This region exists in the presence of a secondary flow which continuously modifies spanwise wall shear stress behavior along the length of the duct.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-1287
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  • 8
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    Flow Coefficient Behavior for Boundary Layer Bleed Holes and Slots (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental investigation into the flow coefficient behavior for nine boundary layer bleed orifice configurations is reported. This test was conducted for the purposes of exploring boundary layer control through mass flow removal and does not address issues of stability bleed. Parametric data consist of bleed region flow coefficient as a function of Mach number, bleed plenum pressure, and bleed orifice geometry. Seven multiple hole configurations and two single slot configurations were tested over a supersonic Mach number range of 1.3 to 2.5 (nominal). Advantages gained by using multiple holes in a bleed region instead of a single spanwise slot are discussed and the issue of modeling an entire array of bleed orifices based on the performance of a single orifice is addressed. Preconditioning the flow approaching a 90 degree inclined (normal) hole configuration resulted in a significant improvement in the performance of the configuration. The same preconditioning caused only subtle changes in performance for a 20 degree inclined (slanted) configuration.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106846 , E-9420 , NAS 1.15:106846 , AIAA PAPER 95-0031 , Aerospace Sciences Meeting and Exhibit; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
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  • 9
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    Experimental investigation of turbulent flow through a circular-to-rectangular transition duct (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 30; 367-375
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  • 10
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    Porous and Microporous Honeycomb Composites as Potential Boundary-Layer Bleed Materials (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Results of an experimental investigation are presented in which the use of porous and microporous honeycomb composite materials is evaluated as an alternate to perforated solid plates for boundary-layer bleed in supersonic aircraft inlets. The terms "porous" and "microporous," respectively, refer to bleed orifice diameters roughly equal to and much less than the displacement thickness of the approach boundary-layer. A Baseline porous solid plate, two porous honeycomb, and three microporous honeycomb configurations are evaluated. The performance of the plates is characterized by the flow coefficient and relative change in boundary-layer profile parameters across the bleed region. The tests were conducted at Mach numbers of 1.27 and 1.98. The results show the porous honeycomb is not as efficient at removing mass compared to the baseline. The microporous plates were about equal to the baseline with one plate demonstrating a significantly higher efficiency. The microporous plates produced significantly fuller boundary-layer profiles downstream of the bleed region for a given mass flow removal rate than either the baseline or the porous honeycomb plates.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA-TM-113160 , NAS 1.15:113160 , AIAA Paper 97-3260 , E-10911 , Joint Propulsion Conference and Exhibit; Jul 06, 1997 - Jul 09, 1997; Seattle, WA; United States
    Format: application/pdf
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