Author: Ing-Jer Chiou
Publisher:
ISBN:
Category :
Languages : en
Pages : 156

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Author: Laurence Byron Wigton
Publisher:
ISBN:
Category :
Languages : en
Pages : 244

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The aim of this thesis is to couple an inviscid two dimensional steady transonic flow calculation with a boundary layer calculation. This interaction is especially important in transonic problems since the boundary layer has a significant effect on the inviscid portion of the flow. Here, the inviscid solution is obtained by an algorithm developed for the full potential equation by Holst and Ballhaus while the attached and separated turbulent boundary layer calculations are performed by Green's lag entrainment method. Guided by a model problem suggested by Le Balleur, a viscous-inviscid coupling algorithm is developed. Theoretical analysis indicates that it coverages rapidly for attached flows ad also performs well for separated flows. These conclusions are confirmed through a series of challenging transonic calculations involving both attached and separated flows. The coupling algorithm is remarkably stable and allows computation of coupled viscous-inviscid flows within times required to perform the inviscid calculations by themselves. (Author).

Author: Chandra S. Vemuru
Publisher:
ISBN:
Category : Laminar flow
Languages : en
Pages : 226

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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781723187162
Category :
Languages : en
Pages : 128

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The viscous/inviscid interaction over transonic airfoils with and without suction is studied. The streamline angle at the edge of the boundary layer is used to couple the viscous and inviscid flows. The potential flow equations are solved for the inviscid flow field. In the shock region, the Euler equations are solved using the method of integral relations. For this, the potential flow solution is used as the initial and boundary conditions. An integral method is used to solve the laminar boundary-layer equations. Since both methods are integral methods, a continuous interaction is allowed between the outer inviscid flow region and the inner viscous flow region. To avoid the Goldstein singularity near the separation point the laminar boundary-layer equations are derived in an inverse form to obtain solution for the flows with small separations. The displacement thickness distribution is specified instead of the usual pressure distribution to solve the boundry-layer equations. The Euler equations are solved for the inviscid flow using the finite volume technique and the coupling is achieved by a surface transpiration model. A method is developed to apply a minimum amount of suction that is required to have an attached flow on the airfoil. The turbulent boundary layer equations are derived using the bi-logarithmic wall law for mass transfer. The results are found to be in good agreement with available experimental data and with the results of other computational methods. Vemuru, C. S. and Tiwari, S. N. Unspecified Center AIRFOILS; BOUNDARY VALUE PROBLEMS; FINITE VOLUME METHOD; SUCTION; TRANSONIC FLOW; BOUNDARY CONDITIONS; FLOW DISTRIBUTION; FLOW VELOCITY; INVISCID FLOW; LAMINAR BOUNDARY LAYER; TURBULENT BOUNDARY LAYER; VISCOUS FLOW...

Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781729430842
Category :
Languages : en
Pages : 44

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This paper presents a method for calculating viscous effects in two- and three-dimensional unsteady transonic flow fields. An integral boundary-layer method for turbulent viscous flow is coupled with the transonic small-disturbance potential equation in a quasi-steady manner. The viscous effects are modeled with Green's lag-entrainment equations for attached flow and an inverse boundary-layer method for flows that involve mild separation. The boundary-layer method is used stripwise to approximate three-dimensional effects. Applications are given for two-dimensional airfoils, aileron buzz, and a wing planform. Comparisons with inviscid calculations, other viscous calculation methods, and experimental data are presented. The results demonstrate that the present technique can economically and accurately calculate unsteady transonic flow fields that have viscous-inviscid interactions with mild flow separation. Howlett, James T. Langley Research Center RTOP 509-10-02-03...

Author: James T. Howlett
Publisher:
ISBN:
Category :
Languages : en
Pages : 44

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Author: R. E. Melnik
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 144

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Author: Tsze C. Tai
Publisher:
ISBN:
Category : Viscous flow
Languages : en
Pages : 58

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The current status of computational capabilities for calculating viscous-inviscid transonic flows other than the solution of Navier-Stokes equations is presented. Techniques for solving transonic inviscid flows and compressible integral boundary layer methods are reviewed, and systems for strong viscous-inviscid interactions are described. Generally, the transonic viscous-inviscid interaction is characterized by a subcritical boundary layer with a supersonic outer stream. The thickening boundary layer produces a pressure rise which causes further thickening of the boundary layer. The physical flow is best modeled by direct coupling of the viscous and inviscid systems to allow immediate interaction between the shock wave and the boundary layer. It appears that the method of integral relations for the outer inviscid flow, combined with an integral boundary layer scheme, possesses such a capability. To facilitate the computation, an hybrid approach to the transonic inviscid solution, which consists of the finite difference method for solving the overall transonic inviscid potential flow field and the method of integral relations for solving Euler's equation in the shock region, is suggested. Finally, the application of the steady two-dimensional methods to the quasi two-dimensional problem on axisymmetric stream surface of a cascade flow at transonic speeds is discussed. (Author).

Author:
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 144

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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