Comparisons of DES and LES Turbulent Model for Simulation of Surface Ship Airwake

Due to the combination of the forward speed and the prevailing wind for surface ship traveling in the ocean, the airflow passing over the ship’s superstructure causes the formation of a disturbed flow region and the large speed gradients of the mean wind over the flight deck, known as the ship airwake. This airwake would cause significant influence on the performance of the helicopter rotor during its taking off or landing, increase the operation workload of the pilot and even cause safe-landing issues, especially when the wind sweeps over the deck. This paper presents a numerical simulation of flow across the ship superstructure using DES and LES turbulent model. The ship model used for simulation is the standard SF2 surface ship model with experimental measurement data which could be used for the CFD code validation. The simulation results are compared with the experimental measurement data, and the comparison with experimental results shows good match for both DES and LES turbulent models. Simulation results show that a series of vortex had been generated after the flow separation with asymmetric characteristics. From upstream to downstream, the vortex intensity decreases, but suddenly increases after encountering the chimney. The comparison between DES and LES turbulent models shows the similar flow field and vortex structure around the ship superstructure with same grid sets. Both DES and LES are superior to RANS in solving ship airwake. The comparisons of DES and LES turbulent models show that DES can reflect the separated flow with limited computational resource and LES simulation could get higher resolution of the fluid flow structure with enough computational resources.