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In this paper, helicopter rotor blades are analysed in hover using computational fluid dynamics (CFD) coupled with a structural model. The method relies on a mesh deformation algorithm that allows for exchange of forces and deformations between a beam-based finite-element model and the fluid flow volume mesh. The method is demonstrated against experimental data, and the aerodynamic predictions appear to improve when the aeroelastic model is used. For all employed cases the flexibility of the method allows the CFD mesh deformation to be spread over the computational domain in a controlled fashion. The influence of the aeroelastic deformations on the blade loads was limited yet evident on the rotor performance. The lack of adequate test cases and experiments for validation of CFD/CSD methods is also highlighted.

CFD predictions of rotor loads and vibration could be improved by resolving a larger part of the turbulent flow spectrum around the rotor. CFD methods, currently in use for rotors blades, employ the URANS approach that is inherently limited in terms of the sizes and frequencies of the resolved local flow structures. This paper attempts to apply hybrid (DES) method of turbulence modelling and simulation aiming to resolve a larger part of the spectrum around rotor blades in hover and forward flight. A comparison between DES and URANS was carried out for the case of a forward flying rotor suggesting that DES has potential for rotor applications. The limitations of the available experiments for CFD validation are also highlighted.

The use of active trailing edge flaps on rotors may lead to performance benefits as well as noise and vibration reduction. In this work, the HMB CFD solver is used, and the trailing edge flaps are modelled using a combination of surface and mesh deformation. Starting from a baseline blade design, the flap is first assessed using dMdt computations, that account for the simultaneous variations of pitch and Mach around the azimuth. It was shown that enhanced lift was obtained while inspection of the moment coefficient showed negative damping for the flap for a limited set of conditions. Due to the 2D formulation, dMdt computations are fast to perform and can be used to inform codes predicting the rotor performance. The flap was then assessed in hover, and only allowed for limited improvement in blade performance at high thrust. In forward flight, the flap was actuated in a 1-per-rev fashion and was found to have a strong effect on the loads on the retreating side. The effect on the moments was even stronger. The flight envelope of the blade was explored, and clean and flapped cases were compared. The most noticeable changes occur at high and medium thrust. The CFD method was found to be efficient and robust, without any substantial penalties in CPU time over the tested conditions. NOMENCLATURE cChord length