Flow Structure of Critical States for a Rolling Delta Wing

Flow visualization tests have been conducted on a 45° delta wing in roll during a high angle-of-attack flight, at the uniform flow velocity of 20m/s. To find the source of their nonlinear roll characteristics. The flow patterns were analyzed by comparing with the results of static aerodynamic force measure-ments. At a roll angle of 15deg, the flow pattern was observed to change from full separation to leading-edge vortex with a vortex breakdown. This change in flow pattern is considered to make a critical state, that is a discontinuity in the characteristics of rolling moment.