[Umro mostafa]

Hi guys
i am working on nanofluid jet impingement simulation
nanofluid mean
water+nanoparticles
i did a simulation considering the nanofluid as a single phase flow
i get some good results
but for more accurate and reality results iwnat to consider two phases flow
i ve to question

1- if gravity must be taken into account in this case ?
when i activate the bouyancy model , the residuals cant get convergence
2-which model aprropriate in this case ?
the geometry with BCs is attached here
thanks

[ghorrocks]

A multiphase model does not sound appropriate for nanoparticles. The models in multiphase models are based on interphase drag. That is not really applicable at the nanoparticle level. Effects such as Brownian motion are more important, and CFX does not have a model for that in the multiphase model.

If the nanoparticles can be modelled as a diffusion effect then multicomponent or even a simple additional variable approach may be adequate.

But overall, CFX does not have the physics to do nanoparticle modelling so it is likely you will not be able to model it on CFX.

[Umro mostafa]

thanks alot sir for your comment
i tried to use Fluent but i get no convergence and when using the CFX for the same mesh i get convergence easily so that i prefer the CFX , i think cfx is more stable than Fluent
please tell me about (((paticle transport solid ))) model in cfx is it not suitable also ?
in the tutorial this model is used to simulate sand particles in water flow in pipes

[ghorrocks]

Please read up about multiphase CFD models. For instance the introduction of the CFX documentation on multiphase models explains this carefully.

Multiphase models are for use where the phases are mixed on the micro-scale. On this scale there is interphase slip leading to interfacial drag forces. Nano-particles are mixed at the nano-scale, there is no interphase slip due to drag forces but there is a whole bunch of new forces - Brownian motion, interfacial chemistry, Van der Waal forces etc. It is not recommended to use a multiphase model to model nano particles as it models different physics.

[Umro mostafa]

Ok i get it
but if the multiphases models in FLUENT is differ from these in CFX ?
cause papers in literature were used multiphases models in FLUENT to simulate the nanofluid
Thanks

[ghorrocks]

Have a look into how appropriate a choice they made then. Just because it is published does not mean it is correct. I have explained why it is a problem so consider the issues I discussed.