EFFICIENT HIGH-RESOLUTION WAKE MODELLING USING THE VORTICITY TRANSPORT EQUATION

Computational Fluid Dynamic models, through their fundamental treatment of the flow physics, present a unique and powerful tool for analysing the aerodynamics of helicopter rotors. Their effectiveness is limited though by their intensive use of computational resources and by their tendency to dissipate vorticity. The Vorticity Transport Model already addresses the problem of vorticity diffusion by solving the fundamental fluid dynamic equations in vorticity conservation form. This paper describes a further development of this model to address the problem of computational efficiency. The new model uses an adaptive grid system to increase grid resolution significantly, with minimal impact on computational cost. The new grid system is effectively boundary-free, thus eliminating the need for numerical boundary conditions at the edges of the computational domain. In addition, the velocity field is optimally evaluated on the new grid using an extremely efficient technique based on the Cartesian Fast Multipole Method. The implementation of both the grid system and the velocity calculation is described, and the performance of the new model is validated against some well-known experimental data.