Abstract

LES (Large eddy simulation) has been used widely in the past decades. It has shown out that more and more advantages comparing with the k-e turbulent model and algebraic stresses model in simulation complication turbulence aspect. In the paper, developing process of LES theory, the elementary theory, application situation and the prospect has been systemic introduced. As study cases, LES theory is applied both in numerical simulation of flow around a square cylinder and momentum jet in the circumstance of linear waves. The typical unsteady flow patterns are giver out for the two cases.

Some typical complex flow phenomena such as separation, vortex shedding, wake formation and growth behind the cylinder were observed from the simulation result. Shedding is periodic and the shedding frequency f depends on both the incoming flow, the size and the shape of the solid body. by the LES model, the momentum jet is glowing from the orifice and to affect the whole depth of water in linear waves. it is found that the waves enlarge the jet area greatly, which is also means that the dilution of the jet is enhanced (J.-M. Chan, H.-H. Hwung, 1993). The enhanced mixing is not only caused by the jet deflection and wave tractive mechanism, but also by the wake vortex. The numerical results have indicated that the LES theory and model have the unique simulation ability for the refined turbulent structure.

Keyword: Large Eddy Simulation , Smagorinsky model , flow around square cylinder, vortex shedding , jet