The Viscous Transonic Flow Over Two-Element Airfoil Systems

The Viscous Transonic Flow Over Two-Element Airfoil Systems
Author: G. Volpe
Publisher:
Total Pages: 49
Release: 1978
Genre:
ISBN:

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A numerical procedure has been developed to compute the transonic viscous-inviscid interacting flow field about airfoils with leading edge slats or trailing edge flaps. The inviscid theory utilizes conformal mappings in a full potential flow formulation, with analytic removal of singularities and a mixed flow relaxation procedure. The turbulent boundary layer is computed with methods based on a turbulent kinetic energy formulation and is coupled to the inviscid flow using surface source flow boundary conditions. Semiempirical methods are used to compute local strong interaction regions occurring in the vicinity of shock waves, trailing edges, and to account for flow separation. Our results are in good agreement with existing wind tunnel data for several typical two-element airfoil configurations. (Author).

Computation of Viscous-Inviscid Interactions

Computation of Viscous-Inviscid Interactions
Author:
Publisher:
Total Pages: 531
Release: 1981
Genre:
ISBN:

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This symposium was consequently organized to review the search for coupling procedures. It appears that the situation is quite satisfactory for 2D flows. Very good correlations can be found between the computational results and the experiments provided that the methods include the wake displacement and curvature effects, and adequate treatment of the trailing edge region and of the shock boundary layer interactions. If so, useful and reliable tools are available for engineering purposes. However, the agreement generally deteriorates with the extension of separated regions or when the shock intensity increases and further improvements are still needed, for example, for single or multielement airfoils near maximum lift or at high Mach numbers. In addition it must be stressed that the quality and the accuracy of the experimental data become questionable as the capability of the computational methods to adequately describe more and more complex situations increases. Therefore precise and reliable code validation requires more and more well documented benchmark data. For 3D configurations, the work is much less advanced; only a few studies have been made and a lot of work has still to be done, especially in the transonic regime. However, the first results obtained using the ideas which have proven to be efficient in 2D are encouraging. The problem of separation with formation and rolling-up of vortex sheets which is specific to 3D flows is of primary importance and the studies already made on this subject will have to be pursued and extended in the compressible and transonic regime. Finally, it has been recorded that the need for detailed benchmark experiments is even greater in 3D than in 2D.

A Viscous/potential Flow Interaction Analysis Method for Multi-element Infinite Swept Wings

A Viscous/potential Flow Interaction Analysis Method for Multi-element Infinite Swept Wings
Author: F. A. Dvorak
Publisher:
Total Pages: 100
Release: 1974
Genre: Aerodynamic load
ISBN:

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An analysis method and computer program have been developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element infinite swept wings in incompressible flow. The wing configuration consisting at the most of a slat, a main element and double slotted flap is represented in the method by a large number of panels. The inviscid pressure distribution about a given configuration in the normal chord direction is determined using a two dimensional potential flow program employing a vortex lattice technique. The boundary layer development over each individual element of the high lift configuration is determined using either integral or finite difference boundary layer techniques. A source distribution is then determined as a function of the calculated boundary layer displacement thickness and pressure distributions. This source distribution is included in the second calculation of the potential flow about the configuration. Once the solution has converged (usually after 2-5 iterations between the potential flow and boundary layer calculations) lift, drag, and pitching moments can be determined as functions of Reynolds number.

Elements of Vorticity Aerodynamics

Elements of Vorticity Aerodynamics
Author: James C. Wu
Publisher: Springer
Total Pages: 147
Release: 2017-12-27
Genre: Technology & Engineering
ISBN: 3662440407

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This book opens with a discussion of the vorticity-dynamic formulation of the low Mach number viscous flow problem. It examines the physical aspects of the velocity and the vorticity fields, their instantaneous relationship, and the transport of vorticity in viscous fluids for steady and unsteady flows. Subsequently, using classical analyses it explores the mathematical aspects of vorticity dynamics and issues of initial and boundary conditions for the viscous flow problem. It also includes the evolution of the vorticity field which surrounds and trails behind airfoils and wings, generalizations of Helmholtz’ vortex theorems and the Biot-Savart Law. The book introduces a theorem that relates the aerodynamic force to the vorticity moment and reviews the applications of the theorem. Further, it presents interpretations of the Kutta-Joukowski theorem and Prandtl’s lifting line theory for vorticity dynamics and discusses wake integral methods. The virtual-mass effect is shown to be the seminal event in unsteady aerodynamics and a simple approach for evaluating virtual-mass forces on the basis of vorticity dynamics is presented. The book presents a modern viewpoint on vorticity dynamics as the framework for understanding and establishing the fundamental principles of viscous and unsteady aerodynamics. It is intended for graduate-level students of classical aerodynamics and researchers exploring the frontiers of fully unsteady and non-streamlined aerodynamics.

Computation of Viscous-Inviscid Interactions (Le Calcul de L'Interaction Fluide Parfait-Fluide Visqueux).

Computation of Viscous-Inviscid Interactions (Le Calcul de L'Interaction Fluide Parfait-Fluide Visqueux).
Author:
Publisher:
Total Pages: 22
Release: 1981
Genre:
ISBN:

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The Symposium surveys the status of current research in computational aerodynamics based on methods solving a viscous-inviscid interaction problem. In spite of limitation in the models or numerical techniques for shock wave boundary layer interaction or trailing edge problems, the situation is well advanced in unseparated, steady two-dimensional flow, with the potential approximation for the inviscid part. Progress has advanced in the computational of separations, based on strong interaction models. It would be fruitful to make use of the complete Euler equations in transonic flow. Progress toward strong interaction methods is much less advanced in unsteady or three-dimensional flow, but seems likely. The development of strong interaction methods, highly connected with that of 'Inviscid' and 'Navier-Stokes' numerical techniques, appears as mandatory to having access to practical application needs.