EAGES 08 - Lifting Line in Extreme Ground Effect - Kirill V. Rozhdestvensky

INTRODUCTION

Kirill V. Rozhdestvensky is a renowned teacher from St Petersburg State Marine University (SMTU), with expertise in ground effect, cavitation, and asymptotic methods. His works extend the approaches of Prandtl to ground effect and provide simple and powerful results. Kirill is an international advocate of ground effect and of SMTU, and was very good at explaining things. During the event, he also kindly helped everyone communicate with his Russian colleagues.

ABSTRACT

The lecture discusses a simplified mathematical model of an ideal fluid flow past a large aspect ratio wing(s) near a solid underlying surface based on the Ludwig Prandtl’s concept of lifting line. With use of the method of matched asymptotic expansions the results are derived in a straightforward manner without solving traditional integro-differential equation(s) for the case of a single lifting line and of a tandem, comprising two wings moving in the same horizontal plane near the ground. The concept implies that the chord of the wing(s) is much smaller than its span. The distance of the lifting line from the ground and longitudinal separation between the wings in the case of the tandem are assumed of the same order as the span. In the limit when relative ground clearance, based on characteristic span of the wing(s), tends to zero, the flow model can be still further simplified through ”quadruplication” of relevant integro-differential equations are reduced to ordinary differential equations of the second order. The latter limiting description of a lifting line or lines in extreme ground effect yields simple analytical formulae for aerodynamic coefficients.

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