Numerical study of effect of hangar modification on ship-airwake and helicopter downwash interaction

Abstract

Numerical investigation of the effects of installing a rotating cylinder at the hangar top edge of a frigate on the dynamic interaction between the airwake generated by a Simplified-Frigate-Ship (SFS) during its propulsion and downwash formed by a 3-bladed helicopter rotor trying to perform landing/take-off operations on the flight deck of SFS is undertaken. The SFS hangar is attached with this rotating cylinder to suffice as an active flow device and the flow field so created by this dynamic interaction is analyzed and compared. The modified frigate is modeled using a scale ratio of 1:100. Measurements are taken in terms of rotor thrust coefficient, recirculation length and turbulence intensity at identified locations. STAR CCM+ code that uses FVM (Finite Volume Method) solver to solve the RANS (Reynolds-Averaged-Navier-Stokes) equation along with two-equation ????? turbulence model as a CFD tool are used for carrying out this numerical analysis. Firstly, the airflow analysis is carried out for SFS-2 in isolation in order to establish a baseline understanding of flow followed by airflow analysis for modified SFS-2, the one equipped with a rotating cylinder. Further, simulations for studying the dynamic interface of ship airwake and the rotor downwash are carried out which involve both the helicopter rotor with ROBIN fuselage and SFS-2 in the first case while the helicopter rotor with ROBIN fuselage and SFS-2 modified with rotating cylinder in the second case. These simulations were varied based upon three distinct cylinder diameter to hangar height ratios for each one of the two rotor hovering -planes positioned parallel to eachother. The inference obtained from this study is that the hangar with a rotating cylinder gives better flow field in terms of recirculation length and thrust co-efficient with zero WOD (wind over deck angle).