Experience with Boundary Element Method to Calculate the Aerodynamic Characteristics of Aircraf

In this paper some experiences with boundary element methods specificly vortex-lattice methods are summarized to calculate the "aerodynamic" characteristics of fixed-wing, rotary-wing aircraft as well as wind turbines. Emphasis is put on influences of vortical flow, e.g. leading-edge vortices of highly swept wings or canard-wing configurations, tipvortices of helicopter or wind-turbine rotors. These vortical flows could cause - among other reasons - the generation of noise. Another source of noise generation could be high speed impulsive noise. Since in this case highly nonlinear compressibility effects are involved this source of noise cannot be treated by linear vortex-lattice method. Therefore, a so-called field-panel method for two-dimensional flow was developed. This method solves the full-potential equation iteratively by solving the Laplace equation by a panel method and the nonlinear part by a field method. The advantage of this procedure is that a very simple rectangular grid can be applied to solve the nonlinear part. In addition, the relatively low cost of panel methods can advantageously be combined with high accuracy of field methods, which are mandatory for transonic flows. It is assumed that these methods, which were - so far - only used to calculate pressure distribution, could further be developed to be used as a basis for calculating several sources of aerodynamic noise generation.