Flow over a cavity during the continued variation of the cavity length
This movie llustrates the process of transformation of the flow structure over the cavity at the continuous change of its length. First, at the increase of the cavity length, the moment of closing of the originally open cavity is observed; then, at the decrease of the cavity length, the closed cavity suddenly opens. The critical length of the cavity closing during the increase of the cavity length is significantly larger than the critical length of the cavity opening during the decrease of the cavity lengh.
Read more in Hysteresis of a supersonic flow around circular cavities.