Computation of Flow over a High-Performance Parafoil Canopy
The incompressible Navier-Stokes equations together with the one equation Spalart-Allmaras turbulence model were solved using a finite volume flow solver to examine the flowfield and forces on the central cross section of a high-performance parafoil canopy. The parafoil surfaces were assumed to be impermeable, rigid, and smooth. The flowfield consists of a vortex inside the parafoil cell opening, which effectively closes off the opening and diverts the flow around the leading edge. The flow about the parafoil experiences a rather bluff leading edge, in contrast to the smooth leading of the baseline airfoil. A separation bubble exists on the lip of the parafoil lower surface. The lift coefficient of the parafoil section increases linearly with the angle of attack up to 8.5 degrees and the parafoil lift-curve slope is about 8% smaller than the same for the baseline airfoil. The cell opening has a major effect on the drag before stall; the parafoil drag is at least twice the baseline airfoil drag. The minimum drag of the parafoil section occurs over the angle-of-attack range of 2.5-7 degrees.