Multi-Level Aerodynamic Engineering Design/Analysis System for Rotorcraft

A number of techniques currently exist for computing rotorcraft aerodynamic flow fields. These range from very fast lifting line schemes which only include the simplest incompressible, inviscid modules for rotor-blades and wake, to full CFD compressible, inviscid potential free-wake methods which are moderately fast, through full compressible Euler/Navier-Stokes methods for rotors and bodies, which are very expensive and have only been used to date for parts of the rotorcraft problem. Currently, there techniques are only used in widely different studies, typically by different engineers, due to the widely different computational speeds and performances of the schemes. A systematic approach is described to combine these techniques into a "multi-level system". The basic idea is that each method will be implemented in a code module which will use essentially the same input and output and appear to a user as almost the same code. Then, the user can easily and quickly do computations for the same problem with different modules, with varying levels of accuracy and speed. This will be very important for rotorcraft engineering design and analysis where a large number of cases (several hundred) must be computed for parametric and optimization studies. Currently, oly very simple, fast codes are used for these studies which lack important aerodynamic effects. With the proposed multi-level system, an engineer will be able to still do a large number of fast runs, typically on a workstation. However, after every set of fast runs, a single, higher fidelity run will be made. The difference in the results between the simple and higher fidelity runs will be used to modify the subsequent set of simple, fast runs so that they include the effects that the simple code, by itself, would have neglected, without greatly increasing the computational time.