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At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Computational Fluid Dynamic Simulation for Electrolyte Flow in Horizontal EP of Nb SRF Elliptical Cavities

An electrolyte flow velocity on an electropolishingsurface affects a material removal rate where higherremoval is observed with a higher velocity of theelectrolyte. In horizontal EP (HEP) of an ellipticalcavity, an electrolyte flow near the equator positionmight remain slow and responsible for a lowerremoval compared to that on the iris and beam pipepositions. In order to understand the flow dynamicon an elliptical cavity surface in the horizontal EPprocess, a computational fluid dynamic simulationwas conducted. This study was conducted on 1.3GHz cavity with different cathodes and acid flowrates. Final aim of the study is to improve the flowuniformity to attain uniform removal especially inmulticell cavities.

Chouhan, V.↗
NASA NTRS1973

Magnetogasdynamic compression of a coaxial plasma accelerator flow for micrometeoroid simulation.

A new configuration of a coaxial plasma accelerator with self-energized magnetic compressor coil attached is described. It is shown that the circuit may be treated theoretically by analyzing an equivalent circuit mesh. The results obtained from the theoretical analysis are shown to compare favorably with the results measured experimentally. Using this accelerator configuration, glass beads of 125-micron diameter were accelerated to velocities as high as 11 km/sec, while 700-micron-diam glass beads were accelerated to velocities as high as 5 km/sec. The velocities are within the hypervelocity regime of meteroids.

Igenbergs, E. B.↗
NASA NTRS1974

Magnetogasdynamic compression of a coaxial plasma accelerator flow for micrometeoroid simulation

A new configuration of a coaxial plasma accelerator with self-energized magnetic compressor coil attached is described. It is shown that the circuit may be treated theoretically by analyzing an equivalent circuit mesh. The results obtained from the theoretical analysis compare favorably with the results measured experimentally. Using this accelerator configuration, glass beads of 125 micron diameter were accelerated to velocities as high as 11 kilometers per second, while 700 micron diameter glass beads were accelerated to velocities as high as 5 kilometers per second. The velocities are within the hypervelocity regime of meteoroids.

Igenbergs, E. B.↗
NASA NTRS1975

Computer simulation of transonic flow past airfoils with boundary layer correction

A computer program has been developed to solve the compressible flow equation for the velocity potential. The exterior of the airfoil is mapped onto the unit circle and the flow is computed on a grid in the circle plane. A relaxation method using backward differencing in the flow direction at supersonic points permits solutions for large supersonic areas. The pressure distribution resulting from the flow becomes the input to the von Karman momentum equation which when integrated gives the displacement thickness. This displacement thickness is smoothed and added to the airfoil to account for the turbulent boundary layer. The boundary layer correction is computed iteratively with the flow. Results from this program and test data agree well.

Bauer, F.↗
NASA NTRS1981

Numerical simulation of reentry flow around the Shuttle Orbiter including real gas effects

The flight environment of a reentry vehicle is predicted from the numerical solution of fluid dynamics equations for the region between the blunt nose and the swept wings. The inviscid portion of the shock layer is modeled by the Euler equations, but the laminar viscous flow adjacent to the wall is modeled by the approximate parabolic Navier-Stokes equations. The approximations made to the axial gradients of pressure and diffusive fluxes enable the coupled inviscid and viscous equations to be solved efficiently along the body axis. The equilibrium air aftbody code contains significant improvements over its predecessor which only considers a perfect gas model and noncircular configurations. The inclusion of numerical damping either explicitly or implicitly has extended its capabilities for predicting flow field around a winged configuration at higher Machs and greater angles of attack. The results are obtained on the cylindrical coordinates and satisfactory for the Shuttle Orbiter at a free-stream Mach number of 22 and an angle of attack of 40 deg. Also discussed are the inviscid formulation and its application for wind-tunnel conditions.

Li, C. P.↗
NASA NTRS1986

Least squares finite element simulation of transonic flows

Finite difference approximation of transonic flow problems is a well-developed and largely successful approach. Nevertheless, there is still a real need to develop finite element methods for applications arising from fluid-structure interactions and problems with complicated boundaries. In this paper a least squares based finite element scheme is introduced. It is shown that, if suitably formulated, such an approach can lead to physically meaningful results. Bottlenecks that arise from such schemes are also discussed.

Chen, T. F.↗
NASA NTRS1985

Numerical simulation of transonic flow over porous airfoils

A numerical study was made to examine the effect of a porous surface on the aerodynamic performance of a transonic airfoil. The pressure jump across the normal shock wave on the upper surface of the airfoil was reduced by making the surface below the shock porous. The weakened shock is preceded by an oblique shock at the upstream end of the porous surface where air is blown out of the cavity. The lambda shock structure shown in the numerical result qualitatively agrees with that observed in the wind tunnel. According to the present analysis, the porous airfoil has a smaller drag and a higher lift than the solid airfoil.

Chow, C.-Y.↗
NASA NTRS1986

Numerical simulation of vortical flow over an elliptical-body missile at high angles of attack

Numerical solutions to the Reynolds-averaged Navier-Stokes equations are given for the flow about an elliptical body missile (3:1 ellipse) at a Mach number of 2.5 and a unit Reynolds number of 6.56 x 10 to the 6th/m. At high angles of attack, the flow is dominated by large-scale free vortices which occur in the lee-side flow field due to crossflow boundary-layer separation. Emphasis is focused on the accurate prediction of the lee-side vortical flow. Solutions are presented for both symmetric and asymmetric (body rolled 45 deg) configurations at 10 deg and 20 deg angle of attack. The computed results are compared with experimental surface pressure coefficients and vapor-screen photographs. Excellent agreement is obtained in all cases.

Newsome, R. N.↗