Considering centrifugal force improves ice accretion simulation on helicopter rotors

In certain areas of the world, weather conditions can cause layered growth of ice on the surface of helicopter rotors. This ice accretion alters the rotor aerodynamics, increasing engine demands and posing a danger to helicopter flight. Most simulations of ice accretion focus on fixed-wing aircraft and therefore don’t consider the effect of centrifugal force, which can be critical in ice accretion on helicopter rotors. Chen et al., however, considered centrifugal and Coriolis forces in simulations that predict the 3D shape of ice accretion on a rotor surface.

The mass of accreted ice can be calculated by simulating the flow and solidification of a thin water film on the rotating curved surface. Here the authors used the Navier-Stokes equations to consider centrifugal and Coriolis forces on water flow. They solved the equations in a body-fitted, non-orthogonal curvilinear coordinate system to obtain the water film velocity. Co-author Ningli Chen explained that the Coriolis force term was found to be negligible.

They combined solutions for the mass-, momentum- and energy-conservation equations to model the final mass of accreted ice. By comparing their results to published experimental data, Chen verified that the model provided a good prediction of water film and ice thickness, even predicting ice profile variations from rotor tip to root. The group then used their model to study how alterations in rotating speed and water droplet diameter effect ice accretion.

“For now we’ve just looked at ice accretion on the rotor, but we also want to look at how this kind of ice affects the rotor dynamics, and how to remove or prevent ice from accreting,” said Chen.

Source: “A three-dimensional mathematical model for simulating ice accretion on helicopter rotors,” by Ningli Chen, Honghu Ji, Guangzhou Cao, and Yaping Hu, Physics of Fluids (2018). The article can be accessed at https://doi.org/10.1063/1.5041896 .