Originally Posted by ghorrocks (Post 486452)

Then I suspect you have defined the nanoparticles as a continuous phase and that does not sound correct.

Can you describe what you are modelling and why you are sure you need a two-phase eularian model for it? For most nanoparticle flow there is no slip of the nanoparticles relative to the continuous fluid, and this means a multiphase model is not appropriate.

Originally Posted by ghorrocks (Post 486591)

What are the nanoparticles? What do they do to the flow? What is the flow? What do you want to compare?

Originally Posted by ghorrocks (Post 494779)

I should write an FAQ on this....

CFX has no nanofluid models. The multiphase model in CFX is a MICRO scale model. It assumes that the lagrangian phase is affected by things like inter-phase slip, particle density and particle mass - these are all micro scale physics. In nano scales things like Brownian motion, surface chemistry, and molecular polarity are important.

So if inter-phase slip, particle density, mass and similar properties are important in your case then you can use CFX's multiphase model.

If you require Brownian motion, surface chemistry, molecular polarity and all these types of nano scale physics then you have to develop the model yourself inside CFX or use some other software.

Particle collision and sticking on the nano scale sounds like Van Der Waal forces to me, along with molecular polarity/ionic stuff. CFX does not have these models, and adding them is not easy (or they would already be in there).

Originally Posted by ghorrocks (Post 494783)

If you are using Fluent then try the Fluent forums.

Fluent has more models available and is more adaptable so you can add your own models. Thsi is probably going to be easier in Fluent than CFX.

Originally Posted by salehorafi (Post 467517)

Thanks for the reply, I'm modelling 2D flow natural convection in a square enclosure utilizing nanofluid in the presence of gravity, the hot and cold walls are 310 and 285 K respectively, the upper and lower walls are adiabatic, the nanofluid is Al2O3 -water based fluid , I'm trying to model the effective thermal conductivity and viscosity and density using mathematical models proposed by recent researchers , the properties will be modeled using UDF as a source code written in C, my question which model should I use? I've heard that some people used the two phase mixture model for modelling the nanofluid, this is an example:
http://www.sciencedirect.com/science...5193313001759#
and another clear example of using two phase mixture model:
http://www.sciencedirect.com/science...0072913001920#
I hope I could explain my case so waiting for explanation and how to use the UDF to model the properties? is the UDF used for both primary and secondary phase or only for the primary phase (water in this case), I've tried both but the contour for temperature looked that no temperature change along the body.
Regards

Originally Posted by ghorrocks (Post 498936)

Have you read any of the posts in this thread? If you have a question about Fluent then try the Fluent forum.