The present study forms an investigation of wake breakdown in hover using the HMB3 solver. Simulations are performed for the PSP rotor blade in hover on a grid aimed at resolving the detailed flow structures in the rotor wake. An assessment of different solver settings is performed including time discretisation, spatial discretisation accuracy and turbulence modelling on the rotor wake resolution and formation of instabilities. A particular focus is put on the existence and resolution of S-shaped structures due to the interactions of the blade tip vortices with the shear layers.

The effect of blade twist on rotor performance is investigated using the Hover Validation Acoustic Baseline (HVAB) and Smart Twisting Active Rotor (STAR) rotors. This is a numerical study conducted using computational fluid dynamics and aeroelastic simulations. The main tool is the Helicopter Multi Block 3 CFD solver of Glasgow. Hover loads are analysed for rigid and elastic cases using a nominal and a higher twist rate. The increased twist did not affect the rotor thrust but increased the hover efficiency. In forward flight, at high-advance ratio, the effect of blade twist was also investigated using aeroelastic computations. A 2-per-rev active twist input was also investigated. Higher blade twist increased vibration in all cases, and reduced performance at high disk loading. The active twist system could achieve increased rotor efficiency and reduced vibration at the studied conditions.

Computational Fluid Dynamics simulations of the Hover Validation and Acoustic Baseline, Smart Twisting Active Rotor, and Active Twist Rotor blades in hover are presented. For these blades, the effect of twist in hover is examined, using the in-house simulation tools of Glasgow University. Rigid and aeroelastic methods are also compared for these rotors. In forward flight, high-twist may be associated with increased blade vibration. For the Smart Twisting Active Rotor blades, the effect of static twist and of a 2/rev harmonic active twist input are also investigated at a high advance forward ratio flight conditions. A vibration index is used to quantify the harmonic components of hub forces and moments. The hover simulations were computed on grids of 10-16m cells, coupled with structural updates. The results show the strong effect of blade twist on hover performance. The forward flight cases were computed on a 36m cell grid and using a modal aeroelastic method.