Signal processor architecture for backscatter radars

Real time signal processing for backscatter radars which requires computational throughput and I/O rates is discussed. The operations that are usually performed in real time are highly repetitive simple accumulations of samples or of products of samples. The control logic does not depend on the values of the data and general purpose computers are not required for the initial high speed processing. The implications of these facts on the architectures of preprocessors for backscatter radars are explored and applied to the design of the Radar Signal Compender

A viscous-inviscid interactive compressor calculations

A viscous-inviscid interactive procedure for subsonic flow is developed and applied to an axial compressor stage. Calculations are carried out on a two-dimensional blade-to-blade region of constant radius assumed to occupy a mid-span location. Hub and tip effects are neglected. The Euler equations are solved by MacCormack's method, a viscous marching procedure is used in the boundary layers and wake, and an iterative interaction scheme is constructed that matches them in a way that incorporates information related to momentum and enthalpy thicknesses as well as the displacement thickness. The calculations are quasi-three-dimensional in the sense that the boundary layer and wake solutions allow for the presence of spanwise (radial) velocities

The effects of stabilizing and destabilizing longitudinal curvature on the structure of turbulent, two-stream mixing layers

The construction and development of the multi-component traversing system and associated control hardware and software are presented. A hydrogen bubble/laser sheet flow visualization technique was developed to visually study the characteristics of the mixing layers. With this technique large-scale rollers arising from the Taylor-Gortler instability and its interaction with the primary Kelvin-Helmholtz structures can be studied

Scramjet nozzle design and analysis as applied to a highly integrated hypersonic research airplane

Engine-nozzle airframe integration at hypersonic speeds was conducted by using a high-speed research aircraft concept as a focus. Recently developed techniques for analysis of scramjet-nozzle exhaust flows provide a realistic analysis of complex forces resulting from the engine-nozzle airframe coupling. By properly integrating the engine-nozzle propulsive system with the airframe, efficient, controlled and stable flight results over a wide speed range

Turbulent boundary layer heat transfer experiments: Convex curvature effects, including introduction and recovery

Heat transfer rates were measured through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20-50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15-20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: (1) the effect of initial boundary layer thickness; (2) the effect of freestream velocity; (3) the effect of freestream acceleration; (4) the effect of unheated starting length; and (5) the effect of the maturity of the boundary layer. Regardless of the initial state, curvature eventually forced the boundary layer into an asymptotic curved condition. The slope, minus one, is believed to be significant

Extraction of Molar Tooth Followed by Necrosis

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Film cooling on a convex wall: Heat transfer and hydrodynamic measurements for full and partial coverage

Turbine-blade cooling is an important issue for high-efficiency turbine engines, and discrete-hole injection is widely used as a cooling method. In the present study, detailed measurements were made of the heat transfer and hydrodynamics of a film-cooled flow on a convex wall, both for full and partial coverage. Two important parameters were altered: the blowing ratio, m, and the number of rows of injection holes. Three values of m were tested: m = 0.2, 0.4, and 0.6. In the blown region, m = 0.4 results in the lowest Stanton numbers of the three blowing ratios tested. This indicates that the value of m = 0.4 is near optimum on the convex wall from the point of view of cooling effect by injection. In the recovery region, Stanton numbers gradually approach the no injection values. Although the heat-transfer behavior during recovery from injection looks relatively complicated, the behavior of Stanton number can be explained in terms of two mechanisms: recovery from the thermal effect of injection and recovery from the turbulence augmentation. This interpretation of the data is supported by the hydrodynamic and temperture-profile measurements. For partial blowing cases, the data follow the full-coverage values inside the blown region. In the unblown region, both in the curved and in the flat plate, the effect of the number of blown rows is clearly seen. Hydrodynamic boundary-layer profiles were measured with the aid of a triple hot-water probe. Three mean-velocity components and six turbulence quantities were simultaneously measured, and inside the blown region strong three-dimensionality was observed

Energy efficient engine: Preliminary design and integration studies

Parametric design and mission evaluations of advanced turbofan configurations were conducted for future transport aircraft application. Economics, environmental suitability and fuel efficiency were investigated and compared with goals set by NASA. Of the candidate engines which included mixed- and separate-flow, direct-drive and geared configurations, an advanced mixed-flow direct-drive configuration was selected for further design and evaluation. All goals were judged to have been met except the acoustic goal. Also conducted was a performance risk analysis and a preliminary aerodynamic design of the 10 stage 23:1 pressure ratio compressor used in the study engines

Metallization of Fluid Hydrogen

The electrical resistivity of liquid hydrogen has been measured at the high dynamic pressures, densities and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) processes in which structural changes are paramount.Comment: 12 pages, RevTeX format. Figures available on request; send mail to: [email protected] To appear: Philosophical Transaction of the Royal Society

An experimental investigation of two large annular diffusers with swirling and distorted inflow

Two annular diffusers downstream of a nacelle-mounted fan were tested for aerodynamic performance, measured in terms of two static pressure recovery parameters (one near the diffuser exit plane and one about three diameters downstream in the settling duct) in the presence of several inflow conditions. The two diffusers each had an inlet diameter of 1.84 m, an area ratio of 2.3, and an equivalent cone angle of 11.5, but were distinguished by centerbodies of different lengths. The dependence of diffuser performance on various combinations of swirling, radially distorted, and/or azimuthally distorted inflow was examined. Swirling flow and distortions in the axial velocity profile in the annulus upstream of the diffuser inlet were caused by the intrinsic flow patterns downstream of a fan in a duct and by artificial intensification of the distortions. Azimuthal distortions or defects were generated by the addition of four artificial devices (screens and fences). Pressure recovery data indicated beneficial effects of both radial distortion (for a limited range of distortion levels) and inflow swirl. Small amounts of azimuthal distortion created by the artificial devices produced only small effects on diffuser performance. A large artificial distortion device was required to produce enough azimuthal flow distortion to significantly degrade the diffuser static pressure recovery