Calculation of Boundary Layers Near the Stagnation Point of an Oscillating Airfoil PDF Download
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Author: Tuncer Cebeci Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
The results of an investigation of boundary layers close to the stagnation point of an oscillating airfoil are reported. Two procedures for generating initial conditions - the characteristics-box scheme and a quasi-static approach - were investigated, and the quasi-static approach was shown to be appropriate provided the initial region was far from any flow separation. With initial conditions generated in this way, the unsteady boundary-layer equations were solved for the flow in the leading-edge region of a NACA 0012 airfoil oscillating from 0 degrees to 5 degrees. Results were obtained for both laminar and turbulent flow, and, in the latter case, the effect of transition was assessed by specifying its occurrence at different locations. The results demonstrate the validity of the numerical scheme and suggest that the procedures should be applied to calculation of the entire flow around oscillating airfoils. (Author).
Author: Tuncer Cebeci Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
The results of an investigation of boundary layers close to the stagnation point of an oscillating airfoil are reported. Two procedures for generating initial conditions - the characteristics-box scheme and a quasi-static approach - were investigated, and the quasi-static approach was shown to be appropriate provided the initial region was far from any flow separation. With initial conditions generated in this way, the unsteady boundary-layer equations were solved for the flow in the leading-edge region of a NACA 0012 airfoil oscillating from 0 degrees to 5 degrees. Results were obtained for both laminar and turbulent flow, and, in the latter case, the effect of transition was assessed by specifying its occurrence at different locations. The results demonstrate the validity of the numerical scheme and suggest that the procedures should be applied to calculation of the entire flow around oscillating airfoils. (Author).
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781724254054 Category : Languages : en Pages : 30
Book Description
A two-point finite difference unsteady laminar and turbulent boundary layer computational method was used to investigate the properties of the flow around an airfoil (NACA 0012) oscillating through angles of attack up to 18 degrees, for reduced frequencies of 0.01 and 0.20. The unsteady potential flow was determined using the unsteady potential flow method of Geissler. The influence of transition location on stal behavior was investigated, using both experimentally determined transition information, and transition located at the pressure peak; the results show the need for viscous-inviscid interaction in future computation of such flows. Cebeci, T. and Carr, L. W. Ames Research Center NASA-TM-85943, A-9599, NAS 1.15:85943, USAAVSCOM-TR-84-A-1 RTOP 505-31-32
Author: Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
The evolution of unsteady boundary layers on oscillating airfoils is investigated by solving the governing equations by the Characteristic Box scheme. The difficulties associated with computing the first profile on a given time-line, and the velocity profiles with partial flow reversal are solved. A sample calculation has been performed for an external velocity distribution typical of those found near the leading edge of thin airfoils. The results demonstrate the viability of the calculation procedure. (Author).
Author: Tuncer Cebeci Publisher: ISBN: Category : Languages : en Pages : 31
Book Description
Recent developments and applications of an interactive boundary layer procedure for unsteady flows are reviewed. The emphasis is on a model problem corresponding to an oscillating thin airfoil in laminar flows and results are reported for different amplitudes and frequencies of oscillation. The use of the characteristic box scheme, with its stability criterion, are shown to allow the accurate calculation of reverse flows and the interaction procedure removes the singularity to allow calculation through regions of separated flow. Although the current focus of the interactive boundary layer procedure has been on the leading edge region, it has general applicability and, together with models for transition and turbulent flows, it can provide the basis for a method to deal with oscillation airfoils and wings and the rapid movement of fixed wing arrangements at angels of attack up to and beyond those of dynamic stall. Calculations at high angles of attack indicate that the behavior of the unsteady separated leading edge flow has similarities to steady flows down-stream of surface corrugations. The use of linear stability theory in the latter case shows that the locations of the onset of transition moves upstream with severity of corrugation and can move inside the separation bubble. In practice this means that the bubbles will be shortened and analogy with unsteady flows suggests that transition may play an important role and preclude the existence of the long separation bubbles determined by the laminar-flow calculations.
Author: Eric Reissner Publisher: ISBN: Category : Aerofoils Languages : en Pages : 44
Book Description
The present report is concerned with the problem of the oscillating airfoil of finite span, within the frame of the linearized lifting surface theory. The aim of this study is the development of a theory which incorporates simultaneously the effects of three-dimensionality of the flow and of compressibility of the fluid. As an exact solution of this problem, even within the limitations of the linearized theory, presents very great difficulties, it is worth while to work toward an approximate theory which is valid provided the aspect ratio of the lifting surface is not too small.
Author: Tuncer Cebeci
Author: Tuncer Cebeci
Author: National Aeronautics and Space Administration (NASA)
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Author: James T. Howlett
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Author: Koji Isogai
Author: Tuncer Cebeci
Author: Eric Reissner
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