New 3-D ice accretion method of hovering rotor including effects of centrifugal force

A new numerical method for predicting 3-D ice accretion on a helicopter rotor in hover is proposed. The new method creatively takes the centrifugal force into account, and the prediction of ice accretion is fulfilled by loosely coupling the novel 3-D icing model with a CFD method. Considering the complexity of ice shapes on a rotor, orthogonally body-fitted grids around rotor blades are generated and modified by solving Poisson equations, and the CFD method for calculating the rotor flowfield in hover is developed by solving Reynolds-averaged Navier–Stokes (RANS) equations and employing the Spalart–Allmaras (S–A) turbulence model. Based upon an embedded grid system around the rotor, an Eulerian method is presented to obtain the water droplet impingement property, and the multistage Runge–Kutta scheme is adopted for temporal discretization. Subsequently, the new 3-D icing model which considers the effect of centrifugal forces is proposed in the freezing process. In this model, the shear stress, pressure gradient and the centrifugal force drive the water film to move on the blade surface. The ice accretion on a UH-1H helicopter rotor in hover is calculated to verify the accuracy of the new method, and the simulated ice shapes on the rotor blade (especially near the blade tip) correlate better with the experimental data than the numerical results of 2-D icing models. Finally, the influence of the centrifugal force in the icing process is analyzed, and numerical results indicate that the total ice amount would decrease when the centrifugal force is taken into account, which have better agreements with the experimental data.