[sadjad]

Hi guys
Is CFX suitable and Feasible for Turbidity Flow or Density Flow?
If Yes, please help me with tutorials and documents.

[ghorrocks]

Turbid flows: yes. Density Flows - what do you mean? If you mean density gradient driven flows (eg salt concentration) then yes.

Exampls are covered by the multiphase and multicomponent example tutorials provided with CFX.

[sadjad]

Thanks "ghorrocks"
About Buoyancy reference density in two phase flow : my model is turbidity flow with water & salty water (density 10 & 15 & 20 gr/lit)
Please guide me to select the suitable value for Buoyancy reference density.

What value is suitable ?

For example : Buoyancy reference density in two phase flow (water flow in empty flum) this value is 1.185 kg/m^3 .

[ghorrocks]

It is just a reference condition, the exact value should not matter. Water density should be fine.

[sadjad]

Then, why this value in other cfx tutorials is variable?
for my model 1.185 is suitable?

[Antanas]

Originally Posted by sadjad

Then, why this value in other cfx tutorials is variable?
for my model 1.185 is suitable?

All answers are in documentation.

For multiphase flows, it can be important to correctly set the buoyancy reference density. For a flow containing a continuous phase and a dilute dispersed phase, you should set the buoyancy reference density to that of the continuous phase. This is because the pressure gradient is nearly hydrostatic, so the reference density of the continuous phase cancels out buoyancy and pressure gradients in the momentum equation.

This is much the same as in single phase, where any non-buoyant calculation implicitly assumes a buoyancy reference density of the fluid, thereby avoiding potential roundoff problems. For non-dilute cases (which include all free surface cases), all terms can be equally important for each fluid, so roundoff errors will be introduced for one of the fluids if there is a significant difference in density. You should choose the density of the lighter fluid because this gives an intuitive interpretation of pressure (that is, constant in the light fluid and hydrostatic in the heavier fluid). This simplifies pressure initial conditions, pressure boundary conditions and force calculations in postprocessing.

[sadjad]

OK. Got it.
Sorry really
I don't understand good English
Then in my model for Buoyancy reference density, i assume density lighter fluid (water : 1000 kg/m^3)
Ok?