Engineering topics

Chow, R. R.

Publications and source records attributed to Chow, R. R..

4 records

NASA NTRS1986

Viscous wing theory development. Volume 1: Analysis, method and results

Viscous transonic flows at large Reynolds numbers over 3-D wings were analyzed using a zonal viscid-inviscid interaction approach. A new numerical AFZ scheme was developed in conjunction with the finite volume formulation for the solution of the inviscid full-potential equation. A special far-field asymptotic boundary condition was developed and a second-order artificial viscosity included for an improved inviscid solution methodology. The integral method was used for the laminar/turbulent boundary layer and 3-D viscous wake calculation. The interaction calculation included the coupling conditions of the source flux due to the wing surface boundary layer, the flux jump due to the viscous wake, and the wake curvature effect. A method was also devised incorporating the 2-D trailing edge strong interaction solution for the normal pressure correction near the trailing edge region. A fully automated computer program was developed to perform the proposed method with one scalar version to be used on an IBM-3081 and two vectorized versions on Cray-1 and Cyber-205 computers.

Chow, R. R.↗

NASA NTRS1986

Viscous wing theory development. Volume 2: GRUMWING computer program user's manual

This report is a user's manual which describes the operation of the computer program, GRUMWING. The program computes the viscous transonic flow over three-dimensional wings using a boundary layer type viscid-inviscid interaction approach. The inviscid solution is obtained by an approximate factorization (AFZ)method for the full potential equation. The boundary layer solution is based on integral entrainment methods.

Chow, R. R.↗

NASA NTRS1985

An improved viscid/inviscid interaction procedure for transonic flow over airfoils

A new interacting boundary layer approach for computing the viscous transonic flow over airfoils is described. The theory includes a complete treatment of viscous interaction effects induced by the wake and accounts for normal pressure gradient effects across the boundary layer near trailing edges. The method is based on systematic expansions of the full Reynolds equation of turbulent flow in the limit of Reynolds numbers, Reynolds infinity. Procedures are developed for incorporating the local trailing edge solution into the numerical solution of the coupled full potential and integral boundary layer equations. Although the theory is strictly applicable to airfoils with cusped or nearly cusped trailing edges and to turbulent boundary layers that remain fully attached to the airfoil surface, the method was successfully applied to more general airfoils and to flows with small separation zones. Comparisons of theoretical solutions with wind tunnel data indicate the present method can accurately predict the section characteristics of airfoils including the absolute levels of drag.

Melnik, R. E.↗

NASA NTRS1985

Solution of viscous transonic flow over wings

Since the calculations of plane steady transonic flows conducted by Murman and Cole (1971), steady progress has been made with respect to the computation of inviscid transonic flows. It has been found that it is inadequate to consider practical wing design at transonic speeds without considering the effects of viscosity and turbulence. The present study has the objective to develop a zonal method for viscous transonic flow over three-dimensional (3-D) wings. The employed approach follows closely the viscous/inviscid interaction techniques discussed by Melnik et al. (1983) for viscous flow about airfoils. Attention is given to inviscid flow equations and boundary conditions, the solution of 3-D boundary layer and wake, an iterative solution to viscid-inviscid interaction analysis, and results obtained for a transonic cruise wing of transport type.

Chow, R. R.↗