In this paper we present scaling results of a FFT library, FFTK, and a pseudospectral code, Tarang, on grid resolutions up to 8192 3 grid using 65536 cores of Blue Gene/P and 196608 cores of Cray XC40 supercomputers. We observe that communication dominates computation, more so on the Cray XC40. The computation time scales as T comp ∼ p −1 , and the communication time as T comm ∼ n −γ2 with γ 2 ranging from 0.7 to 0.9 for Blue Gene/P, and from 0.43 to 0.73 for Cray XC40. FFTK, and the fluid and convection solvers of Tarang exhibit weak as well as strong scaling nearly up to 196608 cores of Cray XC40. We perform a comparative study of the performance on the Blue Gene/P and Cray XC40 clusters.

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In order to reduce the danger of impact onto components caused by break-up, it is important to analyze the shape of shed ice accumulated during flight. In this paper, we will present a 3D finite element method (FEM) to predict the shed ice shape by using a fluid-solid interaction (FSI) approach to determine the loads, and linear fracture mechanics to track crack propagation. Typical icing scenarios for helicopters are analyzed, and the possibility of ice break-up is investigated. NomenclatureE = Young's modulus f, f cf = body force, centrifugal force G = shear modulus h = Neumann boundary conditions LWC = liquid water content MVD = droplet median volume diameter Nvector = normal vector p f = fluid pressure Rvector = propagation vector Tvector = tangential vector u = displacement field v = Poisson's ratio v = Eigen vector  = Cauchy stress tensor ij  = Kronecker delta  i = fluid/structure interface Ω s, Ω f = solid, fluid domain

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