Numerical Simulation Of Flowfield Around Micro Helicopter Rotors

The purpose of this dissertation is to calculate the low speed flowfields of a Micro-helicopter rotor in hover by solving the three dimensional Euler equations corrected by pseudo compressibility. Pseudo compressibility is added to the continuity equation coupling up velocity and pressure. It converts governing equations to a closed system of hyperbolic equations. The solution of Euler equations employ a finite-volume method and 5-stage Runge-Kutta scheme. The technique of local time stepping, pressure damping and implicit residual smoothing are used to increase the convergence rate. The flow around a Micro rotor is calculated and the results agree well with the experiment data. The method given in the dissertation is correct and reliable.The main achievements of this thesis are as follows:1. Referring to compressible method, three-dimensional Euler equations corrected by pseudo compressibility are derived. The eigenvalues of the governing equations' Jacobian matrix are calculated and the stability condition is also presented. According to the Bernoulli equation, similar to compressible calculations, pressure damping is introduced to accelerate convergence.2. The calculation of the flowfield of a hovering rotor is described. In a blade attached coordinate system, the flowfield can be treated as steady case, and the Euler equations are recast in the absolute flow variables so that the absolute flow in the farfield is uniform. The rotational flux due to the rotating frame can be calculated exactly for each cell face using the Stokes theorem.3. The effects of wingtip's speed, angle of attack and the airfoil shape on wing's aerodynamic characteristics are presented. The results of present investigation can instruct the design of a Micro rotor.