Abstract: Numerical methods capable for computing the separated unsteady flow around a double-delta wing are established in this paper. The variation of the dynamic flow fields and aerodynamic performances following the change of the angle of attack is studied, which concentrates on the investigation of the influences of several motion parameters on the time-lag effects of the dynamic flow fields and the hysteresis loops of the aerodynamic coefficients, such as reduced frequency, the position of rotation axis, the averaged angle of attack and the pitching amplitude.The numerical results show that there is great difference in the flow structure between pitch-up and pitch-down states at the same large angle of attack. The time-lag effect caused by the reduced frequency is relatively greater than that by the position of rotation axis. The variation of the averaged angles of attack causes different streamline forms on the leeward side of the double-delta wing; and the span of the streamline forms, which is related to the pitching amplitude, determines how much the dynamic response of the flow structure lags. This numerical analysis is of considerable significance to the understanding of the unsteady characteristics as well as the nonlinear phenomena of a double-delta wing when it pitches upward and downward.

Key words: numerical simulation, double-delta wing, pitching motion, unsteady flow, hysteresis loop