No abstract

Abstract.A noncentered interpolation technique has been constructed to perform simulations using overlapping grids for complex geometries. High-order centered Lagrange polynomial interpolations and interpolations optimized in the Fourier space are first generalized to the noncentered case. These noncentered interpolations either generate significant dispersion errors or strongly amplify high-wavenumber components. Accordingly, a noncentered high-order wavenumber-based optimized interpolation method is developed with the addition of a nonlinear constraint for the control of the amplitude amplification induced by decentering. High-order piecewise polynomial regressions of the obtained interpolation coefficients are performed. The time stability of the method is investigated in the 1-D case when the interpolation method is used in conjunction with explicit high-order differencing, filtering schemes, as well as a 6-step Runge-Kutta time integration algorithm. A criterion is formulated to predict its stability as a function of the filtering strength and the Courant-FriedrichsLewy constant. Finally, 1-D convection simulations are presented to illustrate the stability and the accuracy of the developed noncentered interpolations.

No abstract

No abstract

The present work is part of the Clean Sky 2 project Full-Fairing Rotor Head Aerodynamic Design Optimization (FURADO), which deals with the aerodynamic design optimization of a full-fairing rotor head for the Rapid And Cost-Effective Rotorcraft (RACER) compound helicopter. The rotor head is a major drag source and previous investigations have revealed that the application of rotor head fairings can be an effective drag reduction measure. As part of the full-fairing concept, a new blade-sleeve fairing was aerodynamically optimized for cruise flight. Within this publication, the newly developed blade-sleeve fairing is put to test on an isolated, five-bladed rotor head and compared to an already existing reference blade-sleeve fairing, which was developed at Airbus Helicopters. Numerical flow simulations are performed with ANSYS Fluent 2019 R2 considering a rotating rotor head with cyclic pitch movement. The aerodynamic forces of the isolated rotor head are analyzed to determine the performance benefit of the newly developed blade-sleeve fairing. A drag reduction of 4.7% and a lift increase of 20% are obtained in comparison to the Airbus Helicopters reference configuration. Furthermore, selected surface and flow field quantities are presented to give an overview on the occurring flow phenomena.