In-flight ice accretion simulation in mixed-phase conditions

Abstract

ABSTRACTIcing in conditions where clouds contain both liquid and solid phase particles has attracted considerable interest in recent years due to numerous in-flight incidents including engine rollbacks in the vicinity of deep convective clouds in tropical regions. These incidents have prompted certification authorities to investigate and extend the icing conditions to include solid and mixed-phase clouds for airworthiness certification. These efforts have resulted in the amendments issued by the Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA) to the certification specifications of large aircraft, FAR-25 and CS-25, respectively. Flight tests, laboratory tests and computer simulations are among the acceptable means to show compliance with these specifications. Considerable effort has been spent worldwide in order to develop icing simulation software for liquid phase clouds in the past four decades, but until recently, most of these software did not have the capability for solid- or mixed-phase clouds. One of the aims of the High Altitude Ice Crystals (HAIC) project funded by the European Commission within Framework Program 7 is to address this shortcoming. The present study combines the models related to solid- and mixed-phase icing that is developed within HAIC with an in-house numerical tool. The tool has four modules; a flow-field solution module that uses the Hess-Smith panel method, a module for computing droplet and ice crystal trajectories and collection efficiencies using the Lagrangian approach, a thermodynamic module, and an ice accretion module that utilises the Extended Messinger Model. The numerical tool is tested against experimental test cases including liquid and mixed-phase conditions for various aerofoil and axisymmetric intake geometries. The agreement of the obtained results with experimental data is encouraging.