Turbulence modelling: basic, capabilities and areas of needed research

Abstract

Turbulence modeling is one of the three key elements in Computational Fluid Dynamics (CFD). The other two elements, which are the grid generation and the algorithm development, have been dramatically evolved using very precise mathematical theories. However, this is not the case when it comes to turbulence modeling, in fact, some CFD researchers regard turbulence modeling as the black magic of CFD. The lack of these precise theories in turbulence modeling stems from the ambiguity of the turbulence phenomena itself, indeed, in turbulence modeling, it is tried to mathematically approximate a phenomenon which is not yet physically understood. Scientists started to consider turbulence in fluids more than a century ago. Nowadays, a comprehensive theory for turbulence has been not found yet. However, in this long period of time scientists have produced a huge library of mathematical models that can be used to approximate the physics occurring in a turbulent flow. Most of these models are based on physical reasoning and dimensional analysis, that is, none of these models provide an exact mathematical description of turbulence.