By airlabs
6. December 2021

Project number: 4.404.10001 (CFD-optimisation for drone icing conditions)

Involved cooperation partners:

RTA Rail Tec Arsenal

FH JOANNEUM | University of Applied Sciences

AIRlabs Austria GmbH

Project description/methods:

In addition to the inflow (direction and amount, degree of turbulence), air temperature and icing duration, the size of the water droplets and the water content – referred to as LWC (Liquid Water Content) – are decisive for the icing process on components of aircraft systems. In order to be able to experimentally simulate icing cases for a certification process, it is necessary to be able to determine the LWC. A proven method is the so-called rotating cylinder method. In this method, a cylinder with a defined diameter is positioned transversely in the inflow direction for a certain period of time and rotated at a constant speed. After a certain icing period, the ice mass is determined by a weighing process and the LWC is calculated using an analytical equation. An unknown factor is the so-called collection efficiency, which indicates what percentage of the drops that are on the projected inflow surface of the cylinder actually hit the cylinder. This factor depends on the inflow velocity and the droplet diameter. Depending on the inertia, smaller, lower-mass droplets are more likely to follow the streamlines and not hit the cylinder than larger droplets.

The aim is to create a matrix of collection efficiencies for different diameters and inflow velocities by numerical flow simulations. These results can be used to determine the LWC in experimental icing tests using the rotating cylinder method.


For a total of 4 different inflow velocities and 5 different cylinder diameters, 2D one-way coupled multiphase CFD-simulations were carried out for 9 water droplet sizes using LPT (Lagrangian Particle Tracking). The 180 results of the collection efficiencies were processed as a matrix and clearly presented in diagrams.

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