Frequency Analysis on Canopy Motion and Shock Wave Oscillation around a Hemispherical Wind Tunnel Model of Supersonic Parachute

Frequency analysis of a hemispherical supersonic parachute is performed with dataset obtained by a past campaign of supersonic wind tunnel test. The dataset includes canopy motion and schlieren photographs, which are synchronized with drag data respectively. Lateral instability of the parachute is the target of present study. Influence of canopy motion into drag oscillation is evaluated in terms of power spectral density, while shock oscillation is also compared with the drag oscillation. As results, it is shown that drag oscillation is characterized by two, namely high and low, frequency domains. Drag oscillation can correlate closely with angular motion of parachute canopy in the both frequency domains, whereas canopy motion in different angular direction contributes to each frequency domain. Power spectral density calculated from schlieren photographs also revealed that shock oscillation around the canopy shows different features for the each frequency domain. Consequently, it is successfully demonstrated that frequency analysis of both canopy motion data and schlieren photographs is applicable to describe the lateral instability of supersonic parachute in terms of frequency characteristics.