Computation of transonic flow over elastic rotor blade.

摘要

The understanding of the aeroelastic behavior of transonic rotor blades is essential in the design of advanced vertical-takeoff-and-landing vehicles such as the tilt-rotor and x-wing aircraft. A computational tool is developed in this thesis by coupling an aerodynamic code with a structural dynamic code, which can be used to predict the performance of an elastic rotor blade when operating at transonic speeds.;The full-potential transonic rotor flow code TFAR2, based on the finite-difference approach, is used to compute the inviscid, isentropic and irrotational flow field in a blade-fixed coordinate system. On the other hand, the finite-element approach based on beam theory is employed in the structural dynamic code. Flutter equations are solved in time domain instead of in frequency domain of using modal analysis, and a global-local transformation matrix is derived to improve the accuracy for large blade deflections. The computed natural frequencies of a model blade in the first five modes (three flapping, one lagging and one torsion) agree very well with experimental data.;To demonstrate the capability of this computational tool, both hovering and forward flight cases for the model blade are examined. Numerical results are presented separately to show the differences between rigid and elastic blade calculations. The comparison reveals that the blade elasticity plays an important role in the transonic regime, especially when the rotor is in forward flight.