| A three-dimensional zonal procedure using vorticity and velocity as the computational variables is established. This procedure is the extension of two-dimensional zonal approach, which has been demonstrated as fast, accurate and robust in the numerical calculation of two-dimensional unsteady viscous flows. Through the extension, unique features only existing in the three-dimensional case are identified. Problems associated with such unique features are eliminated. An integral equation which governs normal force distributions on flat plate wings is derived. Numerical techniques to reduce the computational workload in the determination of surface induced velocity are designed. In order to investigate the effect of three-dimensionality on flow characters, a two-dimensional version of the present three-dimensional procedure is formed and validated. In the application of present procedure on flows around flat plate wings, obstacles resulted from the zero-thickness of solid bodies are removed.;Through the computation of viscous flows around stationary flat plate wings, effects of Reynolds number, aspect ratio on flow characters and normal force is observed and discussed. The development of stalled flows on stationary flat plate wings is described and discussed. A change of flow pattern from global separation flow to local separation flow on the leeward side of the flat plate wing is observed and analyzed. The effect of aspect ratio on the slope of normal force and the stall angle is investigated and discussed.;For flows around rapidly pitched flat plate wings, governing equations in the body-fixed reference frame are derived. Through the analysis of flow development during flat plate wing's pitching up motion, substantial delay of stall occurrence is observed. By comparison with two-dimensional stalled flows, it is observed that tip vortex's contribution to the normal force compensates the loss of normal force in the separated middle sections, thus further delays the stall occurrence. |
