Computation of flow over a full-scale ram-air parachute canopy

Includes bibliographical references (pages 96-97)The steady, incompressible Navier-Stokes equations along with the one equation Spalart-Allmaras turbulence model were solved using a finite-volume flow solver, ANSYS Fluent, to simulate the full three-dimensional viscous flow field around a full-scale, rigid, MC-4 canopy model to compute the aerodynamic forces and moments on the canopy. For the zero side slip angle case the surprising aspect of the flow is the non-uniform low velocity regions below the canopy that correspond to the separation bubbles, also a thick boundary layer follows all the way to the trailing edge. The lift coefficient increases linearly with the angle of attack up to 12?? with the lift curve slope of 0.0302 (per deg) and zero lift angle of attack of -4.3??. The lowest drag coefficient occurs at an angle of attack range of 0?? to 2??. The largest lift-to-drag ratio is achieved at 10?? angle of attack. \ud For the non-zero side slip angle case the side force coefficient decreases not quite linearly with the side slip angle; this linear shape is more visible until 10?? side slip angle with the side force curve slope of -0.0048 (per deg) and zero side force angle of 0.15??. Lift coefficient changes are very small with side slip angle. But, the drag coefficient is strongly dependent on the side slip angle; for 20?? side slip angle drag coefficient is 1.4 times the value for zero side slip angle. The pitching moment coefficient increases with side slip angle; for 20?? side slip angle this increase is about 48% compared to zero side slip. The rolling moment coefficient increases nearly linearly until 10?? side slip angle, but after that the curve is not close to linear; the rolling moment coefficient for 20?? side slip angle is 5.7 times the value for 5?? side slip angle. The yawing moment coefficient increases linearly with side slip angle; the yawing moment coefficient for 20?? side slip angle is 3.6 times value for 5?? side slip angle. \ud For the middle range of angle of attacks, the values of lift and drag coefficients are fairly close for the three-dimensional results and the extension of results from a previous two-dimensional study. Although the loads from a 2D study could not be used to accurately predict the loads on a full-scale 3D canopy and result in some error, but they still can provide acceptable assumptions for engineering purposes as a much faster and cheaper method