Swiss/Finnish Computational Fluid Dynamics Simulation on the F/A-18

Since 1995 the Swiss and Finnish Airforces have been operating the F/A-18C/D Hornet as their leading fighter aircraft. Both countries decided to invest in Computational Fluid Dynamics (CFD) simulation tools to study and analyze the flow over the F/A-18. The goal was to develop a modern simulation environment to support the engineering and maintenance of this aircraft, and in particular its structural integrity. In 2005 at the first meeting between RUAG/CFS from Switzerland and Finflo Ltd. from Finland it was decided to perform common research on CFD to improve the grids and solver technology used to simulate the flow over the F/A-18 aircraft. The main objective of these CFD simulations is to provide steady and unsteady loads for engineering investigation as a supplement to the very expensive flight test program. A first series of CFD calculations were carried out in Switzerland for Swiss design load conditions and aerodynamic forces and pressure distributions were compared to the data provided by Boeing from St. Louis. To compare the two non-commercial flow solvers NSMB from Switzerland and FINFLO from Finland the test case M6 wing from ONERA was used. Some differences were observed, which were attributed to the different grids, solution methods and turbulence modeling approaches. In 2010 load cases from the Finish operational loads monitoring program (MINIHOLM) were selected to run CFD calculations. From the CFD results the structural component loads at reference locations were computed. The results obtained for both the Swiss and Finnish grids were excellent and only small differences in component loads were observed.