Emmanuel Guilmineau Researcher EC Nantes

View under the free surface of vorticant structures of the average flow around a skidding boat.

View under the free surface of vorticant structures of instantaneous flow around a skidding boat.

The numerical simulation of the flow of water and air around a skidding boat is a challenge for numerical simulation, namely in predicting the turbulent kinetic energy. When a boat is skidding, a number of vortexing structures are created by the boat’s hull and its appendices and can interact with each other. Experimental measurements have revealed that the level of turbulent kinetic energy was very high at the heart of the eddies. 

Numerical simulations using RANS isotropic turbulence models underestimate this high level. Only simulations using hybrid RANS-LES turbulence models are capable of predicting this high level of turbulent kinetic energy. With this modelling of the turbulence, instationary by nature, the view of the average flow is different. It is the superimposition of small structures that generate the various eddies. The simulations were carried out on a matrix of 163 million cells and used 1,316 processors on the Occigen computer. The Reynolds number for this simulation is 4.65 million. The computing code used was ISIS-CFD, which was entirely developed by the team and resolves the Navier-Stokes equations on non-structured matrices.

This work was carried out as part of the AVT 253 project, an international collaboration under the aegis of NOTA. The work is going to continue with the simulation of the dynamic movement of the boat with a hybrid RANS-LES modelling of the turbulence.