Simulation of the effect of attack angle on ejection and deployment of a parachute

[Objective] Ejection and deployment are the first key actions in the working process of a parachute, thereby resulting in its inflation. Ejection and deployment typically work in the wake of space crafts; therefore, the wake greatly influences the process. The conditions of the free stream may affect the wake flow, such as the attitude, Mach number, and angle of attack. Consequently, the angle of attack of an aircraft is an important consideration in parachute design. [Methods] Ejection and deployment are related to multiple factors, including fluid dynamics, multibody separation, and flexibility deformation. Owing to the advantages of fluid field information and low cost, computation fluid dynamics has become a powerful tool for solving engineering problems regarding fluids. This article focuses on the effect of attack angle on the ejection and deployment of a parachute. Based on the overset grid technology, the three-dimensional unsteady Reynolds averaged Navier-Stokes (URANS) coupled with a six-degrees-of-freedom (6DoF) equation of motion is applied to the research. The simulation consists of two steps: the static flow field simulation and the dynamic separation process based on the static flow field. [Results] The simulation results showed the following: (1) The negative aero force at 0° angle of attack in the recirculation zone hindered the separator department. (2) The wake during the 0° angle of attack was parallel to the axis of capsule; however, 10° and 20° angles of attack demonstrated an obvious deviation from the axis. (3) The separator showed almost no attitude variation for 0° angle of attack, whereas an obvious attitude variation for 10° and 20° angles of attack resulted from the direction of the wake. (4) An obvious interaction occurred between the wake behind the capsule and shock before the separator. [Conclusions] The following conclusions can be drawn from the research: The effects of the angle of attack significantly change the characteristics of the wake. Compared with the 0° condition, the capsule wakes present an asymmetric character in the other two conditions. What's more, the wake shows an obvious deviation from the direction of the initial separated velocity; the asymmetrical wake will affect the trajectory and attitude of the separator; and the effect of the angle of attack will change the relative position between the capsule and the separator and influence the separated time: the time of ejection and deployment will be reduced with an increase in the angle of attack. The method and the conclusions can provide a valuable reference for the validation and design of the recovery system. © 2023 Press of Tsinghua University. All rights reserved.