[mb.pejvak]

In Boussinesq assumption we consider the term derived from convective term and consider it as a diffusion term?

[FMDenaro]

Originally Posted by mb.pejvak

In Boussinesq assumption we consider the term derived from convective term and consider it as a diffusion term?

Are you talking about the turbulence model in the momentum? In such case yes, the unresolved non linear term coming from the convection is converted in a non linear diffusive term

[mb.pejvak]

Originally Posted by FMDenaro

Are you talking about the turbulence model in the momentum? In such case yes, the unresolved non linear term coming from the convection is converted in a non linear diffusive term

Yeah, I am talking about turbulence model in momentum. The question is how we can interpret it. and is there any phenomena in turbulence which convert the convective term into diffusive term or this is only a mathematical assumption.

[LuckyTran]

Originally Posted by mb.pejvak

and is there any phenomena in turbulence which convert the convective term into diffusive term

At the Kolmogorov scales of turbulence, that is exactly what happens.

[FMDenaro]

Originally Posted by mb.pejvak

Yeah, I am talking about turbulence model in momentum. The question is how we can interpret it. and is there any phenomena in turbulence which convert the convective term into diffusive term or this is only a mathematical assumption.

That is a model of a macroscopic observation that the turbulence increases the mixing of a specie. In analogy, this old model convert the fluctuations in an averaged increasing of diffusion of the momentum. However, that is not correct over all the range of scale since the energy transfer has an inertial range at sufficiently high Re number. Furthermore, turbulence can be onset from the convective term, therefore you can idealize also the energy cascade in an inviscid flow. As a consequence, the model will introduce a different mathematical character.