Due to the nature of the fluid-structure interaction, the final shape of the cross parachute should differ between SD and FSI simulations. In the SD simulation, a uniform static pressure was assumed, while in the FSI simulation, the pressure field changed at each time step as data was passed between structural dynamics and fluid dynamics solvers.
The two final geometries did indeed differ, and are shown for comparison below. The SD simulation used 1598 nodes and 1120 two-, three-, and nine-noded elements, while the FSI simulation used an additional tetrahedral fluid mesh with 82142 nodes and 488425 elements.
Initial (Prestressed) Geometry | Final Geometry |
Notice the much more prominent dimpling seen in the final geometry; this additional deformation is due to the uneven pressure field developed during the coupled FSI simulation as opposed to the uniform pressure field used in the SD simulation.
An additional view of the two geometries is shown below.
Initial (Prestressed) Geometry | Final Geometry |
The final simulated geometry shown above is qualitatively similar to the actual geometry of the cross parachute as given by the wind tunnel tests conducted by Parks College. A picture of the actual geometry is given below; more information is available.
Actual Geometry from Parks College Wind Tunnel Tests |