VORTEX-IN-CELL ANALYSIS OF WING WAKE ROLL-UP

A vortex-in-cell (VIC) method was coupled with a wing vortex-lattice m odel to compute steady-state wake roll-up. The vorticity concentrated on the wing and wake vortex segments is distributed to a Cartesian gri d through the application of a spreading function. A subvortex techniq ue is introduced to refine the wake description without altering the n umber of wing panels. The velocity field induced by the spread vortici ty is computed using an infinite domain fast Poisson solver. Interpola tion provides velocities at any point inside the grid. The VIC method is used to compute velocities for a wake relaxation procedure and to c orrect wing panel circulations. The iterative method developed can be applied to configurations with several wings. The method was tested fo r various one- and two-wing problems and compared with results from ex periments and from other theories with very good agreement. Detailed d escriptions for wake geometry and accurate load distributions were obt ained, even for cases where wakes intercepted wings directly.