Maximization of the lift/drag ratio of airfoils with a turbulent boundary layer

The problem of seeking the maximum life/drag ratio for airfoils in an incompressible separationless high-Re flow is considered in the turbulent boundary layer approximation. Within the framework of this model, the maximization of the L/D ratio is redwed to the determination of a conditional extremum for a convex functional. An explicit analytical expression for the extremal solution is obtained. The angle-of-attack dependence of the L/D ratio is demonstrated. The global maximum of the L/D ratio is determined. The results are compared with the known data of numerical optimization. Kazan’. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 177–184, May–June, 1998.