Computation of Unsteady Turbulent Boundary Layer Effects on Unsteady Flow about Airfoils PDF Download
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Author: R. Houwink
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: R. Houwink
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: R. Houwink
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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Author: R. Houwink
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Author: Tuncer Cebeci
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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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: S. J. Shamroth
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ISBN:
Category : Aerodynamics
Languages : en
Pages : 116
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Book Description
A compressible time-dependent procedure for the two-dimensional ensemble averaged Navier-Stokes equations has been applied to the isolated airfoil problem in steady and unsteady flows. The procedure solves the governing equations via the linearized block implicit technique. Turbulence is modeled either via a mixing length or turbulence energy approach. The equations are solved in general non-orthogonal form with no-slip boundary conditions applied at the airfoil surface. Results are presented for airfoils at constant incidence, an airfoil in ramp motion and an airfoil oscillating through a dynamic stall loop. In general, steady converged solutions are obtained within 70 time steps over the range of Mach numbers considered. Comparisons with measured data show good agreement between computation and measurement.
Author: Peter Frederick Lorber
Publisher:
ISBN:
Category :
Languages : en
Pages : 730
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Author: Tuncer Cebeci
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ISBN:
Category :
Languages : en
Pages : 29
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An interactive boundary-layer method previously developed and tested for steady flows is used here in a quasi-steady manner to examine the evolution of the flow behavior of airfoils subject to harmonic oscillation and ramp-type motions. The calculations encompass the airfoil and wake flows at angles of attack which lead to separation. The results quantify the effects of the viscous boundary layer and wake on the variation of lift coefficient with angle of attack and reduced frequency. These effects are shown to be large at angles of attack which involve boundary-layer separation. Keywords: Boundary layer flow; Flow separation; Fluid mechanics; Oscillating airfoils; Stalling; Lift coefficients; Unsteady motion. (edc).
Author: John F. Nash
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 58
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The results are presented of a series of computational experiments aimed at studying the characteristics of time-dependent turbulent boundary layers with embedded reversed-flow regions. A calculation method developed earlier was extended to boundary layers with reversed flows for this purpose. The calculations were performed for an idealized family of external velocity distributions, and covered a range of degrees of unsteadiness. The results confirmed those of previous studies in demonstrating that the point of flow reversal is nonsingular in a time-dependent boundary layer. A singularity was observed to develop downstream of reversal, under certain conditions, accompanied by the breakdown of the boundary-layer approximations. A tentative hypothesis was advanced in an attempt to predict the appearance of the singularity, and is shown to be consistent with the calculated results.
Author: J. E. Yates
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ISBN:
Category : Aerodynamic load
Languages : en
Pages : 24
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Book Description
During the last three years considerable progress has been made in the prediction of unsteady airloads on profiles in transonic flow, but prediction is still limited to potential inviscid flow. New analytical developments, and comparison with experimental results, need the introduction of the coupling between the inviscid flow and the boundary layer. Dr Yates, in this publication, proposes an original approach to the problem which permits a first calculation of boundary layer effects. He derives a new kernel of the lifting surface integral equation which takes into account shear flow effects in the boundary layer.
