布製超音速パラシュートの空力特性

Abstract

Supersonic wind tunnel tests of flexible parachutes whose canopies had a hemispherical shell configuration were conducted. This study was performed to explore the mechanism of flow field oscillation and vibration of canopy movement that were caused by the interaction between the supersonic flow and flexible fabric of the canopies. Effects of the flexibility and gas permeability of fabrics to the drag characteristics of the parachutes were investigated. Three kinds of fabrics (i.e. thin nylon, thick nylon and polyester) were used to produce the canopies. Sizes of canopies were also changed in three steps (nominal diameter D0 = 30, 40, 50[mm]) to investigate the variation of the drag. A load cell was installed in the capsule to measure unsteady and time-averaged drag values of the parachute. Schlieren images by a high speed camera provided us with visualized flow fields showing shock deformations. Moreover, a three-dimensional motion capturing system was used to evaluate the movement of the canopy. The process of parachute ejection from the capsule was also examined. As a result, it was indicated that canopy fabrics with higher gas permeability induce lower mean drag values. On the other hand, the lower flexibility, the larger drag fluctuation is. Furthermore, the spectrum of the canopy movement showed the similar profiles to the spectrum that of the drag fluctuation indicating the direct link between the canopy movement and its drag fluctuation.