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  • 1
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    Viscous wing theory development. Volume 2: GRUMWING computer program user's manual (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: AERODYNAMICS
    Type: NASA-CR-178157 , NAS 1.26:178157 , RE-726-VOL-2
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  • 2
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    Viscous wing theory development. Volume 1: Analysis, method and results (1986)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: 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.
    Keywords: AERODYNAMICS
    Type: NASA-CR-178156 , NAS 1.26:178156 , RE-725-VOL-1
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  • 3
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    An improved viscid/inviscid interaction procedure for transonic flow over airfoils (1985)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: 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.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3805 , NAS 1.26:3805 , RE-682
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  • 4
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    Transonic swept wings studied by the lifting-line theory (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Transonic swept wings are analyzed as a lifting-line problem under a small-disturbance approximation. Basic concepts and principal results of the asymptotic theory are discussed. The study focuses on straight oblique wings and V-shaped swept wings, of which the local centerline curvature can be equated to zero. The three-dimensional (3-D) perturbation of the nonlinear component flow admits a similarity flow structure but requires that all wing sections are generated from a single airfoil profile; the reduced 2-D problems in this case are solved only once for all span stations. Examples of solutions involving high subcritical and slightly supercritical component flows are demonstrated and compared with surface pressure data from 3-D computer codes based on the full-potential equation (FLO 22). Except in the neighborhood of leading edges, where the small-disturbance assumption breaks down, and in the vicinities of wing tips and the symmetry plane, where neither the theory nor the 3-D codes may claim full validity, reasonable agreement is consistently found. The explicit results from the upwash analysis, along with the similarity flow structure, provides a rational approach to the control of 3-D effects in transonic aerodynamic design studies.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Aug. 198
    Format: text
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  • 5
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    Asymptotic theory of two-dimensional trailing-edge flows (1975)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Problems of laminar and turbulent viscous interaction near trailing edges of streamlined bodies are considered. Asymptotic expansions of the Navier-Stokes equations in the limit of large Reynolds numbers are used to describe the local solution near the trailing edge of cusped or nearly cusped airfoils at small angles of attack in compressible flow. A complicated inverse iterative procedure, involving finite-difference solutions of the triple-deck equations coupled with asymptotic solutions of the boundary values, is used to accurately solve the viscous interaction problem. Results are given for the correction to the boundary-layer solution for drag of a finite flat plate at zero angle of attack and for the viscous correction to the lift of an airfoil at incidence. A rational asymptotic theory is developed for treating turbulent interactions near trailing edges and is shown to lead to a multilayer structure of turbulent boundary layers. The flow over most of the boundary layer is described by a Lighthill model of inviscid rotational flow. The main features of the model are discussed and a sample solution for the skin friction is obtained and compared with the data of Schubauer and Klebanoff for a turbulent flow in a moderately large adverse pressure gradient.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Aerodynamic Analysis Requiring Advanced Computers, Pt. 1; p 177-249
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  • 6
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    Transonic swept-wing analysis using asymptotic and other numerical methods (1980)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper presents asymptotic methods for high-aspect-ratio wings in transonic flow developed for straight unyawed wings and for oblique wings. They show that the three-dimensional mixed-flow calculations may be reduced to solving a set of two-dimensional problems at each span station; the development of this theory and the related computational studies are reviewed. Differences between the piloted (oblique) wing, the swept-back wing, and the swept-forward-wing in the induced upwash are discussed; examples of similarity solutions are demonstrated for high subcritical and slightly supercritical component flows, and comparisons made with relaxation solutions of a full potential equation. The examples include oblique and symmetric swept wings, and the adequacy of the existing full-potential computer code is examined.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-0342 , Aerospace Sciences Meeting; Jan 14, 1980 - Jan 16, 1980; Pasadena, CA
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  • 7
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    Theory of viscous transonic flow over airfoils at high Reynolds number (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper considers viscous flows with unseparated turbulent boundary layers over two-dimensional airfoils at transonic speeds. Conventional theoretical methods are based on boundary layer formulations which do not account for the effect of the curved wake and static pressure variations across the boundary layer in the trailing edge region. In this investigation an extended viscous theory is developed that accounts for both effects. The theory is based on a rational analysis of the strong turbulent interaction at airfoil trailing edges. The method of matched asymptotic expansions is employed to develop formal series solutions of the full Reynolds equations in the limit of Reynolds numbers tending to infinity. Procedures are developed for combining the local trailing edge solution with numerical methods for solving the full potential flow and boundary layer equations. Theoretical results indicate that conventional boundary layer methods account for only about 50% of the viscous effect on lift, the remaining contribution arising from wake curvature and normal pressure gradient effects.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-680 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 8
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    Numerical solutions of the triple-deck equations for laminar trailing-edge stall (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The problem of determining the effect of laminar boundary layers on the lift of thin wings in subsonic flow at high Reynolds numbers is considered. The boundary value problem is formulated in the framework of the triple-deck theory of Brown and Stewartson. The resulting fourth-order boundary value was solved by an iterative finite-difference technique. An inverse iteration procedure provides proper treatment of the trailing-edge singularity, and asymptotic far-field expansions and coordinate stretchings are used to deal with the problem of the slow algebraic decay of the solution.
    Keywords: AERODYNAMICS
    Type: International Conference on Numerical Methods in Fluid Dynamics; Jun 28, 1976 - Jul 02, 1976; Enschede; Netherlands
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  • 9
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    Solution of viscous transonic flow over wings (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: 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.
    Keywords: AERODYNAMICS
    Type: Computers and Fluids (ISSN 0045-7930); 13; 3 19
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