A series of Computational Fluid Dynamic (CFD) studies have been performed on a WC-135B aircraft that has been modified at Wright-Patterson AFB (WPAFB) for the Open Skies program. The studies included use of a panel method, full potential method, and Navier Stokes methods in 2-D, axisymmetric, and 3-D. While providing information useful to the Open Skies program, the studies also provide a good example of how lower order and higher order computational aerodynamic methods can be used together to obtain the maximum benefit from CFD.
The panel method was used for numerous trade studies to help determine the proper configuration and conditions for the Navier Stokes studies. It also provided for early indications of potential problems that could arise from the Open Skies configuration. As a result, it was also used to test out modifications to the baseline Open Skies contours that were developed in order to minimize the possibility of shock formation over the Open Skies pod.
The full potential computation provided a 3-D look at possible shocks and supporting information on one of the panel method trade studies. The Navier Stokes studies were performed in an incremental approach. A coarse grid was first run on the full fuselage, followed by 2-D and axisymmetric representations of the aircraft centerline using both the coarse and fine grids. The axisymmetric study revealed separation and a weak shock while the 3-D fine grid Navier Stokes study predicted there would be no shock at all. Flight test confirmed the 3-D Navier Stokes results.