The initial stages of two-dimensional unsteady leading-edge boundary-layer separation of laminar subsonic flow over a pitching NACA-0012 airfoil have been studied numerically at Reynold number (based on airfoil chord length) Rec = 10000, Mach number Munendlich = 0,2 and nondimensional pitch rate Omega+0=0,2. Computations have been performed using two separate algorithms for the compressible laminar Navier-Stokes equations. The first method, denoted the structured grid algorithm, utilizes a structured, boundary-fitted C grid and employs the implicit approximate-factorization algorithm of Beam and Warming. The second method, denoted the unstructured grid algorithm, utilizes an unstructured grid of triangles and employs the flux-difference splitting method of Roe and a discrete representation of Gauss'theorem for the inviscid and viscous terms, respectively. Both algorithms are second-order accurate in space and time and have been extensively validated through comparison with analytical and previous numerical results for a variety of problems. The results show the emergence of a primary clockwise-rotating recirculating region near the leading edge which can be traced to a pair of critical points (a centre and a saddle) that appears within the flowfield, followed by a secondary counter-clockwise-rotating recirculating region and a tertiary clockwise-rotating recirculating region. The primary and secondary recirculating regions interact with each other to give rise to the unsteady separation (Breakaway) of the boundary layer.


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    Title :

    Two-dimensional unsteady leading-edge separation on a pitching airfoil


    Additional title:

    Zweidimensionale instationäre Strömungstrennung an der Vorderkante eines sich verstellenden Rotorblatts


    Contributors:

    Published in:

    AIAA Journal ; 32 , 4 ; 673-681


    Publication date :

    1994


    Size :

    9 Seiten, 17 Bilder, 2 Tabellen, 50 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English