Dispersed Multiphase: Airfoil Icing

When aircraft pass through air containing supercooled liquid water droplets, it is possible for the droplets to impact the aircraft surface and form layers of ice. Ice formation on an aircraft wing changes the aerodynamic properties of the wing, and leads to loss of lift, increase in drag, and a change in pressure distribution. Simcenter STAR-CCM+ provides a technique for simulating the formation of ice on airfoils. This technique relies on the Dispersed Multiphase model to represent the liquid droplets in the air surrounding the airfoil.

The case simulated in this tutorial consists of a two-dimensional airfoil in an icing tunnel. The case is taken from a NASA study ([979]) on ice formation and icing effects for modern airfoils.

In this simulation, a multiphase mixture of air and water droplets flows over an idealized two-dimensional airfoil, in a low-temperature, low-turbulence regime. The mixture flows with initial velocity of 129 m/s in the x-direction. The droplets are water particles with diameter of 2.1E-5 m. The droplets volume fraction, with respect to air, is of 3.42E-7.

The geometry that is used in the tutorial is displayed below.

In the DMP method, the background air affects the water droplets through drag and heat transfer. The water droplets, however, do not have any impact on the air. The liquid content of the droplet phase is transferred to the surface of the airfoil as a liquid film. For this reason, a shell region with fluid film properties is created on the surface of the airfoil. Droplets impact the shell region and form a liquid film.

Liquid film on the airfoil surface turns to ice. As more and more ice is formed, the shape of the airfoil must change. Simcenter STAR-CCM+ converts the volume of ice in the film to a corresponding deformation in the wing surface. After deforming the wing surface using the mesh morpher, Simcenter STAR-CCM+ removes the volume of ice from the film layer. In this way, the shape of the shell region changes to reflect the buildup of ice on the airfoil surface.