Freestream

About: Freestream is a research topic. Over the lifetime, 3428 publications have been published within this topic receiving 56147 citations.

An experimental investigation of a jet issuing from a wing in crossflow.

Abstract: The aerodynamic interference resulting from a jet issuing normal to the chordal plane of a twodimensional wing in a crossflow has been experimentally investigated. Measurements of the interference surface pressure distribution on the wing and of the wing interference force and moment coefficients have been made for a systematic variation of jet exit location, jet exit diameter, wing angle-of-attack, and the ratio of jet exit velocity to freestream velocity, A. A comparison of the contours of constant interference surface pressure on the wing lower surface with those for an infinite flat plate reveals that they are much the same for A > 6. The dissimilarity becomes greater as X is decreased, primarily through the growth of an extensive region of positive interference surface pressure forward of the jet on the wing. Interference lift losses of approximately the same magnitude for all geometries were observed for X > 6. However, a lift augmentation occurred for X < 6 which was attenuated by increases in angle-of-attack, forward movement of the jet exit location, and decreases in jet exit size. The data indicate that the character of the interference flow is distinctly different for high and low values of the velocity ratio.

Aerodynamic Heating to Corrugation Stiffened Structures in Thick Turbulent Boundary Layers

Abstract: The results of an experimental program to evaluate heat transfer and pressure distributions on corrugation roughened flat plates in thick turbulent boundary layers are presented. The experimental program consisted of tests in the tunnel wall boundary layers of the Langley Unitary Plan Wind Tunnel (UPWT) and Continuous Flow Hypersonic Tunnel (CFHT) at freestream Mach numbers of 2.5, 3.5, 4.5, and 10.3. Tests in the UPWT were conducted at a freestream Reynolds number/m of 10.8 x 106 and in the CFHT, at Reynolds numbers/m of 1.3 to 5.8 x 106. The test configurations consisted of 50.8 cm x 50.8 cm panels with corrugated beads of two different peak amplitudes, 0.61 cm and 0.29 cm. The angle of the corrugated beads relative to the flow direction was varied between 0° (aligned) and 90° (normal). The measured peak and average heat transfer are analyzed and correlated in terms of the bulk boundary layer, internal boundary layer, and geometric parameters. The data are also compared with similar data for thinner boundary layers, and with previously published correlation techniques.

Simulation of transonic viscous flow over a fighter-like configuration including inlet

Abstract: The simulation of transonic viscous flow over a modified F-16A including inlet is presented. A zonal approach is utilized which allows appropriate clustering suitable for viscous calculations on all solid surfaces. Computational efficiency is enhanced by solving the thin-layer Navier-Stokes equations in viscous zones adjacent to the aircraft and the Euler equations on those coarse zones away from the aircraft. The flow conditions for this transonic case are freestream Mach number of 0.9, angle of attack of 4.12 deg, and a Reynolds number (based on root chord) of 4.5 million. A total of 19 zones are utilized yielding a total of 350,000 grid points. This case required about 3000 iterations to reduce the residual by three orders, which takes about 10 hr of CPU time on the Cray X-MP/48 computer. Pressure distributions on the wing and on cross sections through the inlet region compare favorably with the experimental data for this transonic case.

Hypersonic-finite rate chemically reacting viscous flows over an ablating carbon surface

Abstract: Hypersonic finite-rate chemically reacting viscous flows over an ablating carbon surface have been analyzed using the viscous shock-layer method to study the effects of ablating carbon on the surface-measurable quantities and on the electron density, temperature, and species profiles across the shock layer. The results for nonequilibrium air injection and the ablating carbon surface mass transfer were compared. Of all the test cases considered, the ablating carbon case shows an approximately 10°7o higher stagnation heat-transfer rate than the equivalent nonequilibrium air injection case. The effects of fully catalytic, noncatalytic, and equilibrium catalytic wall boundary conditions were also compared to analyze the effects of catalytic wall boundary conditions on the heat-transfer rate. At low wall temperatures, such as 1000 K, the noncatalytic wall condition showed the lowest heat-transfer rate. However, at high wall temperatures (such as 3333 K) due to the positive wall diffusion heat transfer, the equilibrium catalytic wall condition showed the lowest heat-transfer rate at an altitude of 84 km and a freestream velocity of 7.6 km/s. A method for analyzing nonequilibrium finite-rate chemically reacting flows over multiconic geometries with ablating carbon surface has been developed.