AeroCFD: Fin CFD Analysis (OPTIONAL): Back
A fin CFD analysis, not part of the Euler CFD analysis, is automatically performed when the user clicks the SOLVE button in the Solution Controls region on the main screen.To perform a manual fin CFD enter the Fin CFD Analysis screen by clicking on the sixth icon from the left on the main screen toolbar. Fins are meshed using the node numbers generated on the Free-Form Fin Geometry screen. The first node on the fin-root chord [a] and the second node on the fin-root chord [b] are automatically displayed in the Fin Data region. Perform the following operations when attempting to modify the Fin CFD parameters.

a) Input the first node number that defines the leading edge of the fin-tip chord [c] and then the second node number that defines the trailing edge of the fin-tip chord [d] is automatically displayed in the Fin Mesh Controls region.

b) Input the total number of grid points in the X [axial] and Y [up] directions. Depending on the complexity of the fin shape, the user may need to adjust the total number of grid points in the X and Y directions and the starting node for the fin-tip chord to generate a uniform and solvable fin mesh.

c) Solve the Fin CFD by clicking the SOLVE command button in the Solution Controls region in the Fin CFD Analysis screen.

d) By default AeroCFD computes the flow on the windward side of the fin after clicking the SOLVE command button in the Solution Controls region on the main screen. If the flow on the leeward side of the fin is required or if the fin grid density needs to be modified then the user needs to manually select the option button in the Solution Controls region and then SOLVE the fin CFD using the new parameters in the FIN CFD Analysis screen. In addition, by default the fin mesh size is 25 X 25 unless modified in the Mesh Controls region and then SOLVE'd in the Solution Controls region. There is no need to solve the main flow CFD again. Simply, click back to the Plot screen and plot the fin mesh and fin surface contours without having to SOLVE the main CFD again.

Background: For subsonic flow this analysis uses thin-airfoil (fin) vortex-sheet theory to determine the pressure distribution (P/Pinf), pressure coefficient distribution (Cp), Mach number distribution (Mn), density distribution (R/Rinf) and temperature distribution (T/Tinf) on the surface of the fin. The Prandtl-Glauert compressibility factor, SQR(1-Minf^2) is used to convert airfoil vortex-theory results to compressible flow results for velocity up to Mach 0.80. For supersonic flow the windward surface distributions are computed using the oblique-shock wave relationships for thin fins. Finally, for supersonic flow the leeward surface distributions are computed using the Prandtl-Meyer expansion wave relationships for thin fins.