Numerical simulations of wake structure generated by rotatingblades using a time marching, free vortex blob method

摘要

Vorticity fields in the wake generated by rotating blades arecalculated using a time accurate, free vortex blob method without a nonphysical model of the far wake. The computed free wake geometry ofsingle rotor in hover is represented by the three wake regions: welldefined tip vortex region, intermediate entangled region, and initiallygenerated wake bundle. The air loads and simulated wake geometries inthe radial and axial directions agree well with those obtained using aprescribed wake method for a one blade rotor, and with the experimentaldata for a two blade rotor. This agreement can be obtained with thecorrect initial condition of a slowly rotating blade instead of animpulsively rotating blade. The wake geometry and unsteady air loads ofhelicopter rotor in forward flight is also calculated in forward flight.The rotor blade and wake interaction is critical to vibration and noiseproblem of the helicopter. Because the computational time of the freevortex blob method is proportional to the square of the element number,the reduction method of computational time is also considered