Numerical simulation of the effect of the permeability on the ringsail parachute in terminal descent stage

For the study of the influence of permeability of fabric on aerodynamic performance of parachute, the permeability of fabric is described by the Ergun equation and introduced into the source term, establishing a new governing equation of flow momentum with the permeability of fabric fully considered.The numerical solution is get and compared with the traditional result, in which the influence of permeability of fabric was ignored. The result shows that the velocity penetrating the fabric can be obtained through the new flow field momentum equation and it's obviously lower than the velocity of the flow through the surrounding holes and that around the parachute. The first wake vortex region which clings to the canopy and the second wake vortex region which consists of a pair of center points are in the wake of the canopy, the permeability of fabric makes the first wake vortex region longer, the number of the vortex points increase and the distribution of the vortex more uniform and symmetrical. It also decreases the size of the second wake vortex, which improves the stability of the canopy through a shorter and narrower whole wake vortex region. Besides, the permeability of fabric decreases the pressure inside the canopy, increases the pressure outside. The pressure coefficient of the canopy in the radial direction decreases, thus, the drag coefficient of the new model is lower than the traditional model, which is closer to the results of the airdrop experiments. Obviously, the new model is significant to improve the accuracy of flow field simulation around the porous canopy.