A new time-marching free vortex method applied for calculation on rotor aerodynamic characteristics

A new time-marching free vortex method for calculation on rotor wake and induced velocities is developed.In this method,a new 2-step 2-order accurate predictor-corrector with backward difference algorithm-named D2PC is deduced.In order to increase the accuracy of the solution for rotor wake,the discrete approximation of vortex governing equation using D2PC algorithm is modified and improved.Based on the Vatistas formula,the vortex core model is given which is under the consideration of vortex diffusion.The blade is simulated by the simplified lift-surfacing model,in which the determining method on blade bound vorticity strength is re-derived.In the free vortex method,the blade flap model and trimming model are also combined.By the comparisons of calculated results with experimental results for some numerical examples on wake geometries and induced velocities,the present free vortex method is validated.Then using the method,characteristics on rotor wake geometries and induced velocities for hover and forward flight are calculated and analyzed.