十字形伞有限质量充气展开及尾流再附现象

Finite Mass Inflation and Wake Recontact Phenomenon of Cross Parachutes

为探究折叠十字形伞有限质量充气特性及尾流再附现象,采用任意拉格朗日-欧拉方法对质量比数M_(r)范围为0.17~0.94以及弗劳德数F_(r)范围为6.8~383.9的十字形伞-载荷系统减速过程进行流固耦合数值模拟。研究M_(r)及F_(r)对十字形伞充气过程的影响,并讨论其对开伞载荷峰值Xp、伞衣坍塌参数R_(c)的影响,绘制十字形伞“正常充气展开”、“发生尾流再附后再次充气”、“发生尾流再附后完全失效”3种不同充气展开结果关于M_(r)及F_(r)的相图。分别对3种十字形伞的充气现象进行详细分析,研究其开伞载荷、阻力系数及伞衣投影直径的瞬态变化过程。结合伞衣结构变形、伞衣应力及非定常流场,阐明十字形伞3种不同充气展开过程的流固耦合机理。研究结果表明:无量纲开伞载荷峰值X_(p)及坍塌参数R_(c)随F_(r)的增大而增大;十字形伞有限质量充气展开过程中,伞衣与周围空气发生较为剧烈的动量交换,可能出现高速尾流与伞衣接触导致十字形伞明显凹陷甚至完全塌陷失效的现象。

The finite mass inflation characteristics and wake recontact phenomenon of folded cross parachutes are investigated.The fluid-structure interaction numerical simulation is conducted using the arbitrary Lagrangian-Eulerian(ALE)method for the cross parachute-load system with mass ratio from 0.17 to 0.94 and Froude number from 6.8 to 383.9 during deceleration.The effects of the mass ratio and Froude number on the inflation process of cross parachute are studied.The peak deployment load and canopy collapse parameter are discussed.The phase diagrams for the three different inflation results of cross parachute,namely,normal inflation,reinflation after wake recontact,and complete failure after wake recontact,are plotted in relation to the mass ratio and Froude number.The three inflation processes of cross parachute are analyzed in detail.The deployment load,drag coefficient,and transient change in the projected diameter of canopy are studied,and the fluid-structure interaction mechanisms of different inflation processes are studied by taking into account the structural deformation of parachute,stress distribution and unsteady flow field.The results indicate hat the dimensionless peak deployment load and canopy collapse parameter increase with the increase in Froude number.During the finite mass inflation process of parachute,there is intense momentum exchange between the canopy and air around it,which may lead to high-speed wake flow interacting with the canopy to cause a significant collapse or even complete collapse of the cross parachute.