Prediction of Maneuvering and Stability Derivatives

All AFT RANS methods are time-accurate, and can therefore be used for unsteady simulations normally thought beyond the demands of traditional design applications.  Whether a body is fixed or moving, time-accurate forces are accurately resolved and can be used to predict unsteady lift and drag, rigid-body motion, or structural deflection.   AFT has used the approach to develop models for the efficiency of “swimming fish” propulsion methods, control of “flapping wing” micro-air vehicles, and to populate stability and control derivative matrices of towed arrays. 

For cases where relative motion is required (e.g. body deflections, multi-body problems, free-fall trajectories) a mixture of body-fixed and Earth-fixed grid blocks are used.  The overset grid cutting is updated at every time step, and inter-block communication is provided by a time-accurate interpolations scheme.  Run-time efficiency is maintained using time-adaptive algorithms to identify those portions of grid that require reprocessing at each time step.  Click on a menu item at left to see examples of how AFT uses its unsteady RANS capabilities.