A new computational method for computing flow over complex aerodynamic configurations and its application to rotor/body computation using cartesian grids

A new numerical method for efficiently computing vortex-dominated flows over complex aerodynamic configurations is developed . This method uses only a fixed, uniform Cartesian grid, no body conforming grid is required. The complex geometry surface is described by a smooth scalar function "F", which is defined at each grid node. By using Vorticity Confinement, this method effectively confines the vorticity to a narrow region even on coarse computational grids and for low order discretization schemes. The flow both inside and outside the configuration is considered, although in aerodynamic applications, the internal flow is fictitious. The no-slip boundary condition is imposed on solid body surfaces by eliminating the flow inside the configuration. Unlike other general Cartesian methods, no specific logic is needed to determine the body surface in the present method. Also, the vorticity can be shed from smooth surface as well as surfaces with sharp corners. Vorticity Confinement involves adding a simple term to the Navier-Stokes fluid dynamic equations. When discretized and solved, these modified equations admit convecting, concentrated vortices which maintain a fixed size and do not spread, even if there is numerical diffusion. Numerical results are presented for flows around simple and complex con figurations which were investigated with the present method. As an application of this method, preliminary numerical flow solutions of a combined helicopter blade and real helicopter body are presented. The code developed in the present method uses a relatively coarse, fixed. Cartesian grid and requires much less computing time compared to high order accurate flow solvers, while capturing the vorticity efficiently and accurately. The code will be very useful for engineering analysis and design of aircraft as well as automobile.