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The Prediction of C l max Using a Separated Flow Model

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A method for calculating the flow about airfoils up to and beyond the stall is described. It is an iterative procedure between potential flow and boundary layer solutions. The separated region is modeled in the potential flow analysis using free vortex sheets which require an inner iteration to establish their shapes. The free vortex sheet length is an important parameter in the potential flow calculation. Results so far indicate a possible correlation between wake length and airfoil thickness/chord ratio and a tentative curve is presented here. Calculated and experimental results are compared for a GA(W)‐l airfoil at two Reynolds, numbers, 6.3 × 106 and 2.1 × 106. and for a NACA 4412 airfoil over a range of Reynolds numbers. The calculated results, which include pressure distributions as well as force and moment characteristics, are in very close agreement with experimental results and are obtained for reasonable computing costs; typically, one incidence data point takes 15 to 20 c.p. seconds an the CDC 7600 computer.

Document Type: Research Article


Affiliations: Analytical Methods, Inc., Bellevue, Washington

Publication date: April 1, 1978

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  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

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