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
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.