Study of Geometric Porosity on Static Stability and Drag using Computational Fluid Dynamics for Rigid Parachute Shapes

Abstract

This paper explores use of computational fluid dynamics to study the e↵ect of geometric porosity on static stability and drag for NASA's Multi-Purpose Crew Vehicle main parachute. Both of these aerodynamic characteristics are of interest to in parachute design, and computational methods promise designers the ability to perform detailed parametric studies and other design iterations with a level of control previously unobtainable using ground or flight testing. The approach presented here uses a canopy structural analysis code to define the inflated parachute shapes on which structured computational grids are generated. These grids are used by the computational fluid dynamics code OVERFLOW and are modeled as rigid, impermeable bodies for this analysis. Comparisons to Apollo drop test data is shown as preliminary validation of the technique. Results include several parametric sweeps through design variables in order to better understand the trade between static stability and drag. Finally, designs that maximize static stability with a minimal loss in drag are suggested for further study in subscale ground and flight testing.

Aerodynamic simulation and analysis of large ring-sail parachute

“…The reliability of the numerical method is verified by comparing the drag coefficient with the literature [12] for different angles of attack. The simulation results of the drag coefficient variation with angle of attack are given in Fig.…”

“…Tutt et al [6] used the ALE method of LS-DYNA software to simulate the main parachute of two North American airborne system candidates, the Advanced Tactical Parachute System (ATPS), one of which is a square parachute and the other is a round parachute; Xiaojuan Shang et al [7] numerically simulated the inflation process of a ring-sail parachute with a draft-top parachute using a fluid-solid coupling calculation method; Takizawa et al [8] numerically simulated the ring-sail parachute of the Orion spacecraft using a fluid-solid coupling (FSI) method to observe its breathing, gliding and oscillation, and proved that the breathing characteristics of the parachute are caused by vortex shedding, the breathing amplitude is related to the head angle, and increasing the hanger length ratio will increase the projection area, thus increasing the drag, etc. ; Tutt et al [9] used the fluid-solid coupling method in LS-DYNA to simulate a 7-foot diameter flat circular parachute and a 5-foot circular seam parachute and compared them with experimental results; Cheng Han et al [10] used the ALE method to numerically simulate the deployment process of a fully folded parachute; Lian Liang et al [11] used the ALE method to numerically simulate the steady descent phase of the Apollo parachute recovery system, studied the flow-solid coupling process of three ringsail parachutes, and simulated the shape change of the parachute and the change of the flow field inside and outside the canopy; Greathouse et al [12] studied the effect of geometric porosity on the static stability and drag of the MPCV main parachute through numerical simulation. Chen et al [13] conducted a numerical study of the effect of incoming Mach number and parachute fabric permeability on the complex flow and aerodynamic characteristics of the parachute system based on computational fluid methods using a rigid model of a scaled-down Mars Science Laboratory disk seam belt parachute.…”

Sub-Scale Orion Parachute Test Results From the National Full-Scale Aerodynamics Complex 80- by 120-ft Wind Tunnel

“…Based on pre-test studies using CFD, 4 it was expected that blockage and wall-effects would affect the parachute motion and overall aerodynamics. In addition, the dynamic aerodynamic performance between the sub-scale testing and full-scale drop tests was expected to be different due to scaling.…”

“…In evaluating potential design changes, the team considered many factors including previous design updates to Apollo and Orbiter 5 parachutes that provided improved stability, CFD predictions, 4 and the experience and engineering judgment of parachute experts. The team was also careful to consider potential effects on the performance of the nominal 3-main parachute system, as the pendulum motion was only seen in a contingency 2-main parachute scenario, as well as ensuring that any design changes would not hinder the ability to apply the results of previous full-scale drop testing to evaluation of the final design.…”