Developments in computational methods for high-lift aerodynamics

Abstract

SummaryViscous/inviscid interaction techniques for calculating the flow about multiple-element aerofoils have been under development in the UK for the last decade producing such programs as MAVIS and HILDA. These methods give reasonable predictions of the lift for viscous attached flow, but fail to give an estimate of the maximum lift and the associated flow separations on the aerofoils. The methods also fail to give adequate predictions of the drag for both attached and separated flow. The disappointing performance of the methods in predicting maximum lift stems primarily from the use of direct methods to solve the first order boundary-layer equations, whilst the poor drag predictions arise from inadequate methods for predicting the development of the flow over the flap. The assumption of incompressible flow could also be a contributory factor in both cases. Methods of overcoming the first restriction are described by using a more appropriate coupling between the inviscid and viscous flows which properly assigns the correct role to each partner in the coupling: this approach is illustrated by ‘semi-inverse’ and ‘quasi-simultaneous’ couplings of a finite-element method for the compressible inviscid flow with an integral method for the boundary layers and wakes. Some methods for calculating the compressible flow about multiple-element aerofoils are also reviewed. However these improvements do not give an adequate estimate of the drag so possible improvements to the calculation of the flow over the flap are discussed.