Numerical Simulations of Wake Structure Generated by Rotati a Time Marching, Free Vortex Blob

Vorticity fields in the wake generated by rotating blades are calculated using a time-accurate, free vortex blob method without a non-physical model of the far wake. 77~ compuredfree-wake geomeby of single rotor in hover is represented by the three wake regions: well-defined tip vortex region, intermediate entangled region, and initially generated wake bundle. The air loads and simulated wake geometries in the radial and aria1 directions agree well with those obtained using a prescribed make method for a one-blade rotor, and with the experimental data for a two-blade rotor. This agreement can be obtained with the correct initial condition of a slowly rotating blade instead of a impulsively rotating blade. 13ie wke goemeby and unsteady air loads of helicopter rotor in forwardjlight is also calculated In forward jlight, the rotor blade and wake interaction is critical to vibration and noise problem of helicopter. Because the computational time of the free vortex blob method is proposional to the squre of element number, the reduction method of computational time is also considered