Simulation of Flowfield Around a Ram-Air Personnel Parachute Canopy

Abstract

The flowfield around a model MC-4 ram-air personnel parachute canopy was examined using the steady, incompressible Navier–Stokes equations together with the one-equation Spalart–Allmaras turbulence model. A finite volume flow solver was used to compute the flowfield, forces, and moments on the canopy in steady glide and at sideslip. The canopy surfaces were assumed to be impermeable and rigid. The oncoming flow barely penetrates the canopy opening, and creates a large separation bubble below the lower lip of each half-cell. The flow does not reattach, and a thick boundary layer is present on the lower surface of the canopy. The flow over the upper surface of the canopy remains attached until the separation point near the trailing edge. The lift increases linearly with the angle of attack up to about 12 deg, whereas the quarter-chord pitching moment decreases nearly linearly between 2 and 12 deg angle of attack. For sideslip angles up to 20 deg, the side force increases linearly with the sideslip angle even as the lift remains nearly constant. The yawing moment also increases linearly with the sideslip angle, whereas the rolling moment varies quadratically. The fidelity of the lifting-line theory in predicting the forces on the canopy during steady glide was assessed.