Dear Arun,

Turbulence is the state of a fluid, liquid or gas, in which the speed present at any point a swirling character : vortices whose size, location and orientation constantly vary. Turbulent flows are therefore characterized by a very messy appearance, unpredictable behavior and the existence of many spatial and temporal scales. Such flows appear when the kinetic energy source which sets the fluid in motion is relatively intense compared to viscous forces that the fluid opposes to move. Conversely, laminar character called a regular flow. The discovery and study of turbulence is very old, it was done for example by Leonardo da Vinci. To reflect the fact that, in a flow, the inertial forces outweigh the viscous forces, a Reynolds number suitably chosen must be greater than a certain threshold. For the study of turbulence in a natural environment it is best to use the Richardson number rather than Reynolds, because it considers the fluid density as constant, which is not true in the case of compressible fluids.

With my best regards

Prof. Bachir ACHOUR

Depending on the presence of external source of kinetic energy, turbulence can decay or reach a statistical equilibrium. Transitional increasing is possible if  production and dissipation do not balance each other.

" Doing one CFD simulation" means nothing... what formulation you want (or need) to use? DNS, LES, (U)RANS are very different formulation used in the CFD field.

The choice strongly depends on the type of flow problem and the goal of the study.

I am interested in one simple case where turbulence is controlled by a passive devise and how to quantify that . I'm looking for one paper deals with this. For simple cases I can go upto LES.

Thank you. 

Forcing parameter can also increase the turbulence intensity such as turbulent shear mixing layer.