Simulation of simplified frigate using embedded LES turbulence model: Part-I validation and turbulence scales

Abstract

Understanding and characterization of turbulence over the flight deck of large marine vehicle is important to assess its influence on the helicopter pilot workload while performing launch and recovery maneuvers. This research is regarding understanding the turbulent flow field over the flight deck of simplified frigate model (SFS2) using an Embedded Large Eddy Simulation turbulence model in which a portion of flow field that is of interest is resolved using LES model, thereby reducing the overall computational cost. The influence of placement of RANS-LES interface is explored and detailed validation of the numerical scheme suggests that it can capture the turbulent flow structure, especially bi-stable air wake over the flight deck of SFS2 at the zero-yaw flow condition, with better accuracy. The development of downstream air wake into the far field is also discussed. Once the numerical scheme is validated, the characterization of integral time and length scales of turbulent vortical structures in the superstructure air wake is carried out using single point correlations. It is observed that flow field at flight deck center is influenced by vortices shed from top of superstructure and funnel whereas its edges towards port and starboard sides are predominantly affected by superstructure edge vortices.