Assessment of the Vortex Feature-Based Vorticity Confinement Method Applied to Rotor Aerodynamics and Aeroacoustics

The accurate prediction of helicopter rotor aerodynamics and aeroacoustics using Computational Fluid Dynamics (CFD) techniques still remains a challenge, as the over-dissipation numerical schemes results in higher diffusive rate wake vortices than what can be expected from fluid governing equations. To alleviate this issue, vortex feature-based vorticity confinement (FVC2-L2) method that combines locally normalized λ2 detection with standard second (VC2) scheme is presented to counterbalance truncation error introduced by discretization convective term while avoiding over-confinement inside boundary layer. FVC2-L2 adopted for aerodynamic aeroacoustic predictions through its implementation multi-block structured grid CFD solver ROSITA coupling code ROCAAP based on permeable surface Ffowcs Williams–Hawkings (PS-FWH) equation. This approach assessed flows via three databases. Firstly, well-documented HART-II baseline condition used evaluate capability VC blade–vortex interaction (BVI) phenomena prediction. Subsequently, UH-1H non-lifting hovering AH-1/OLS low-speed descending flight are assessment such aeroacoustics. benefits terms prediction, preservation, noise signal well demonstrated comparison experimental data obtained without schemes. Particularly, mainly improves highly unsteady airloads an improvement BVI more 5 dB respect case case. Additionally, some shortcomings noticed engineering applications. On basis simplified vortex, provisional guidelines required εo value number cells per diameter provided: ranging 0.01 0.04 grids which may represent core 6 12 cells.