The impact of icing on performance is not only relevant for external aircraft parts (wing leading edge icing, ram air inlet icing) but also affects internal systems such as those responsible for aircraft ventilation. The mechanisms leading to icing for such internal flows differs to that for external flows. Hence, although a variety of simulation tools are available for aircraft external icing, they are not necessarily applicable for the prediction of internal icing.

Since the impact of accumulated ice on performance (added weight, pressure loss, etc.) and safety (structural damage, exceeded load limits, etc.) is non-negligible for aircraft air generation systems, a bespoke simulation methodology has been developed to predict the accumulation and effects of ice in internal 3D air flows. Features of this method include:

• Prediction of ice build-up for realistic timeframes (several hours)
• Prediction of first ice locations
• Prediction of critical icing areas
• Direct computation of accumulated mass of ice
• Calculation of pressure loss due to ice build-up

Comparisons between CFD predictions and experimental tests show a promising match. Consequently, the availability of a reliable and efficient icing prediction tool for virtual product development offers many benefits. These include the ability to achieve improved and robust system design and the optimisation of control-software for de-icing systems.