Determination of Influence Boundaries in CFD from Acoustic Intensity Distribution

Using influence region technique in CFD has the advantage of simpler grid generation, fast computing time, and the facility of multiple equation sets or multiple flow solvers. We propose to develop a first principal based, graphic interactive method for the determination of influence boundaries. We will use combined a) theoretical, b) numerical solution to acoustic equation, c) correlation function; and d) rule of thumb to determine the influence boundaries. Since theoretical solutions and empirical correlations are only valid for the simple geometries and flow conditions, the proposed fast acoustic equation solver will be more fundamentally sound and reliable. In the current approach, with given free stream Mach number, angles of attack, and model geometry, a CFD solution based on coarse mesh and simple physical model will be solved along with acoustic wave equation. Isotropic value of the acoustic intensity from the solution will be used to quantify the influence regions. In Phase I, a numerical solution to the acoustic equation with high order scheme will be implemented in an existing unstructured, solution adaptive CFD-Solver with overset grid capability. The feasibility of the wave intensity factor as physics base for the determination of influence boundaries will be explored by comparing with theoretical solution and empirical correlation. In Phase II interactive software to enable the visualization and analysis of computed flowfield solutions to be used as a guide in creation of the influence boundaries will be developed. Future verification and simulation of realistic complex air vehicle geometries using influence region method will be carried out, and the developed module and its implementation in other DoD CFD codes such AVUS will also be carried out in Phase II.