Helium Bubble Survey of a Parachute Opening Flowfield

A velocity survey of the flow field surrounding an 18 inch nominal diameter flat circular parachute model was made using the helium bubble technique. Due to asymmetrical model behavior arising from optical limitations, only two points in the filling cycle were examined. The point at which the canopy first reaches full open instant at which inflation is complete and at a time late in the cycle when steady state flow conditions are reached. Bubble streaks were photographed by two synchronized, orthogonally mounted still cameras, and the particle velocities were calculated using the measured lengths of the images and the camera exposure times. Although the canopy geometries at the two points considered were quite similar, their surrounding flow fields were not.