In this paper, a computational study of the DTU 10MW reference wind turbine unsteady aerodynamics is presented. The whole wind turbine assembly was considered, including the complete rotor and the tower. The FINE/Turbo flow solver developed by NUMECA International was employed for the simulations. In particular, the Non‐Linear Harmonic (NLH) method was applied in order to accurately model flow unsteadiness at reduced computational cost. Important vortex shedding structures were identified at low blade span range and all along the tower height. A strong interaction between rotor and tower flows was also observed. Lastly, the performance of the NLH approach was compared against a standard Unsteady Reynolds‐Averaged Navier Stokes simulation. The same complex unsteady flow phenomena were captured by both technologies. Nevertheless, the NLH approach was found to be 10 times faster than the Unsteady Reynolds‐Averaged Navier Stokes method for this particular application. Copyright © 2016 John Wiley & Sons, Ltd.

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A new method for fluid‐structure interaction (FSI) predictions is here introduced, based on a reduced-order model (ROM) for the structure, described by its mode shapes and natural frequencies. A linear structure is assumed as well as Rayleigh damping. A two-way coupling between the fluid and the structure is ensured by a loosely coupling staggered approach: the aerodynamic loads computed by the flow solver are used to determine the deformations from the modal equations, which are sent back to the flow solver. The method is first applied to a clamped beam oscillating under the effect of von Karman vortices. The results are compared to a full-order model. Then a flutter application is considered on the AGARD wing 445.6. Finally, the modal approach is applied to the aeroelastic behavior of an axial compressor stage. The influence of passing rotor blade wakes on the downstream stator blades is investigated.

The nonlinear harmonic method (NLH) and its extension to the modeling of the clocking effects can simulate the unsteady flows in multistage machines at drastically reduced CPU costs. The blade row interactions that are reproduced are those between adjacent rotors and stators and also between successive rotors or successive stators. At an additional level of complexity, it appears that in stator1 / rotor / stator2 configurations the amplitude of the perturbation associated with a blade passing frequency (BPF) in a row is not only created by the adjacent row but is also modified in space by the interaction of the periodic disturbances coming from the other two rows. For instance, the spatial modes of the periodic disturbance in stator2 are provoked not only by the interaction with the adjacent rotor but also by an additional interaction with the periodic flow coming from stator1. The present paper introduces a method that enables the identification of these modes for a general configuration row1 / row2 / row3. Any row can be a stator or a rotor and the time-varying disturbances are not only produced by the interaction with the adjacent row but also with the other rows. In particular, this is validated and illustrated for the calculation of the unsteady effects provoked in contra-rotating open rotors (CROR) by the engine pylon. Results are also shown for stator/rotor/stator configurations that shows the effects of clocking on the time harmonics.