TDLM - A Transonic Doublet Lattice Method for 3D Potential Unsteady Transonic Flow Calculation.

Kurzfassung

In this report, a Transonic Doublet Lattice Method (TDLM) for calculating unsteady transonic pressure distributions and airloads isdeveloped. The flow around harmonically oscillating surfaces is described by superposition of a steady transonic mean flow and an unsteady harmonic flow. The unsteady flow component is modelled by acceleration potential doublets on the mean wing surface and a source distribution in the flow field near the wing. The time-linearized unsteady transonic small perturbation equation is solved by an integral equation method. Results for a rectangular wing, the Northrop F-5 wing, and the LANN wing in pitching oscillation are presented. Comparisons are made with both experimental and other numerical results. Agreement with the experimental results is very good. The computing time on the IBM 3090 is less than ten minutes for one reduced frequency, and it shows that the TDLM can provide a sufficiently accurate and cost-effective procedure for routine transonic flutter calculations.