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The applicability of FENSAP-ICE-Unsteady to solve ice accretion on rotating helicopter blades is investigated using a two-bladed rotor and a generic cylinder, to represent a fuselage, for a forward flight test case. The unsteady rime ice accretion is simulated by coupling, at each time step, flow and water drop equations to the Messinger icing model. Mesh displacement effects are taken into account by an Arbitrary Lagrangian-Eulerian method. This new icing model is applied to rotor/fuselage flows by considering two grid domains: the first being fixed around the fuselage, and the second rotating with the blades. The gap region is stitched with tetrahedral elements to fully guarantee flow conservation.

In order to ensure flight safety in icing conditions and meet FAA or other national aircraft certification regulations, which require an aircraft to be able to safely operate throughout the icing envelope of Part 25 Appendix C, ice protection mechanisms have to be employed on critical locations of an aircraft. Among different anti-icing mechanisms, hot bleed air systems are the most reliable and efficient ones, and are widely used on commercial aircraft to protect critical surfaces such as leading edge wing panels and high lift devices, empennage surfaces and engine nacelle lip. Due to the complexity of anti-icing experiments and flight tests, advanced numerical simulation of complex thermal anti-icing systems has been highly anticipated as a supplementary design and certification tool. CHT3D [1], the new 3-D Conjugate Heat transfer module of FENSAP-ICE [2] for the simulation of hot air and electrothermal ice protection, will be presented in this paper.

A numerical approach to the trajectory simulation of break-up ice in the in-flight icing code FENSAP-ICE is investigated. At each time step, the displacement and rotation of the moving domains is computed from a 6-DOFs analysis of the forces and moments. The moving domains are amalgamated into the fixed background mesh by a hole-cutting and stitching algorithm, producing a continuous unstructured hybrid mesh, eliminating interpolation between domains and ensuring that the fluxes are fully conserved across the entire mesh. To maintain good load balancing on parallel computers, the finite element CFD flow solver uses an efficient parallel iterative matrix solver and domain decomposition to partition the computational domain into equal-sized subdomains. Test cases used to validate and demonstrate the features of the computational algorithm are shown.

The FENSAP-ICE system was first conceived for fixed-wing aircraft and air induction system icing, but major developments are underway to augment its capabilities for icing simulation of rotorcraft and tiltrotor aircraft. A project is underway, under the auspices of the RITA (Rotorcraft Industry Technology Association) to reduce icing certification flight tests through use of second-generation three-dimensional (3D) Computational Fluid Dynamics (CFD) based technologies. The plan is to supplement traditional icing tunnel and flight-testing with modern 3D inflight icing simulation tools that facilitate the development and certification of all-weather operations rotorcraft and tilt-rotor aircraft. A viscous fully 3D ice accretion and runback modeling capability is being developed and initial correlation studies to both 2D and 3D icing test cases have produced very good results.

Numerical in-flight icing simulations have become a powerful tool in the type-certification process of commercial aircraft, helping to focus and reduce the number of flights in natural icing conditions and icing wind tunnel tests. Despite the numerical software's sophistication, applicants should always validate it for various icing conditions, and show good predictability to the aviation authorities. Icing being a key certification issue for the design of such aircraft because of its direct link to flight safety, MHI (Mitsubishi Heavy Industries) has early on adopted FENSAP-ICE and integrated this 3-D icing software into its Regional Jet program. The objective of this paper is to validate, on geometries of significance to MHI, this numerical tool for accuracy in predicting the flow field, droplet impingement and ice shapes. This step is required prior to integrating the software in the actual design process.