A Numerical Study of Viscous Flows Around Airfoils PDF Download
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Author: J. C. Wu Publisher: ISBN: Category : Aerofoils Languages : en Pages : 36
Book Description
The application of an integro-differential approach in the numerical study of unsteady viscous flows about airfoils is described. Two different procedures are presented. A procedure based on a stream function-vorticity formulation and on a transformation technique is used in a study of a flow about an impulsively started 9% thick Joukowski airfoil at an angle of attack of 15 deg and a Reynolds number of 1000. Numerical results are presented and compared with available finite-difference results. A second procedure based on a velocity-vorticity formulation and on a hybrid finite difference-finite element technique is used in a study of a flow about an oscillating 12% thick Joukowski airfoil at a Reynolds number of 1000. With either procedure, the unique ability of the integro-differential approach to confine the solution field to the vortical region of the flow is utilized. It is shown that this ability offers great computational advantages. (Author).
Author: J. C. Wu Publisher: ISBN: Category : Aerofoils Languages : en Pages : 36
Book Description
The application of an integro-differential approach in the numerical study of unsteady viscous flows about airfoils is described. Two different procedures are presented. A procedure based on a stream function-vorticity formulation and on a transformation technique is used in a study of a flow about an impulsively started 9% thick Joukowski airfoil at an angle of attack of 15 deg and a Reynolds number of 1000. Numerical results are presented and compared with available finite-difference results. A second procedure based on a velocity-vorticity formulation and on a hybrid finite difference-finite element technique is used in a study of a flow about an oscillating 12% thick Joukowski airfoil at a Reynolds number of 1000. With either procedure, the unique ability of the integro-differential approach to confine the solution field to the vortical region of the flow is utilized. It is shown that this ability offers great computational advantages. (Author).
Author: James C. Wu Publisher: Springer ISBN: 3662440407 Category : Technology & Engineering Languages : en Pages : 147
Book Description
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.
Author: Miguel A. Ortiz Publisher: ISBN: Category : Languages : en Pages : 37
Book Description
Investigation of steady and unsteady flowfields over airfoils is an active area of current computational and experimental research. In this study, the compressible, viscous, flow over a single and multi-element airfoil is numerically simulated by solving the Navier Stokes equations. The motivation for this work includes interest in studying the effects of a stationary/flapping airfoil combination in tandem configuration. A single-block Navier-Stokes (NS) solver is employed to compute unsteady flowfields. Turbulence is treated using the Baldwin-Lomax turbulence model. A single C-grid is generated and it is partially distorted to simulate the flapping motion. Numerical solutions are obtained for flows at a fixed angle of attack and for unsteady flows over flapping airfoils. The numerical solutions agree well with the experimental data The difficulties faced during the study are discussed and future improvements are suggested.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722672980 Category : Languages : en Pages : 82
Book Description
A new two-dimensional computer code was developed to analyze the viscous flow around unconventional airfoils at various Mach numbers and angles of attack. The Navier-Stokes equations are solved using an implicit, upwind, finite-volume scheme. Both laminar and turbulent flows can be computed. A new nonequilibrium turbulence closure model was developed for computing turbulent flows. This two-layer eddy viscosity model was motivated by the success of the Johnson-King model in separated flow regions. The influence of history effects are described by an ordinary differential equation developed from the turbulent kinetic energy equation. The performance of the present code was evaluated by solving the flow around three airfoils using the Reynolds time-averaged Navier-Stokes equations. Excellent results were obtained for both attached and separated flows about the NACA 0012 airfoil, the RAE 2822 airfoil, and the Integrated Technology A 153W airfoil. Based on the comparison of the numerical solutions with the available experimental data, it is concluded that the present code in conjunction with the new nonequilibrium turbulence model gives excellent results. Ahmed, S. and Tannehill, J. C. Unspecified Center...
Author: J. C. Wu
Author: J. C. Wu
Author: C. M. Wang
Author: Sarangan Sampath
Author: James C. Wu
Author: Angela Yit Lean Cheer
Author: A. Y. Cheer
Author: Vincent DeHenau
Author: Miguel A. Ortiz
Author: National Aeronautics and Space Administration (NASA)
Author: Thomas J. Coakley