CFD Online Discussion Forums - *Urgent*Pressure Inlet Bundary Condition Error*Urgent*

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)

- FLUENT (https://www.cfd-online.com/Forums/fluent/)

- - *Urgent*Pressure Inlet Bundary Condition Error*Urgent* (https://www.cfd-online.com/Forums/fluent/79423-urgent-pressure-inlet-bundary-condition-error-urgent.html)

*Urgent*Pressure Inlet Bundary Condition Error*Urgent*

Dear all
I have a question about reversed flow error in pressure inlet boundary condition. I am modeling flow of water in a simple channel (only one faze). I have 4 boundary conditions, velocity inlet, pressure inlet for free surface, wall and pressure outlet for outlet. I know that I can use symmetry boundary instead of pressure inlet for free surface, but I want to know why the results of velocity filed of these two cases are different each others?
Let me to ask my question in another way, can I use pressure-inlet boundary condition for free surface of water or not? If I can please explain for me why the flow is reversed and how I can fix this error?
I hope some nice persons help me.
Best Regards,
Farhad

Hi, Farhad,
Free surface can not be simulated by pressure inlet. A problem fall into the category of open channel flow, a multiphase flow, if it involves free surface of two phases. In FLUENT, VOF model can be used for this.

Hi Xrs333
Thanks a lot for your reply.
According to your reply I mention some points and questions, please answer them:

1- I know that the VOF model can model free surface, but I do not want to model the free surface. I want modeling only region under free surface. The interface of two faze is not important for me (My free surface has not any fluctuation).

2- In fact I want to model the sedimentation in a sedimentation tank (settling tank). I have mixture of water and sand in a tank and there is a free surface at above. My main problem is that which boundary conditions must be applied for it? Is pressure inlet done?

3- Can I use Eulerian model for 3 faze (water, sand and air) or must be used a two faze model and a boundary conditions for free surface?

4- Is it possible using pressure inlet for free surface and 2 faze instead of modeling 3 faze in Eulerian model?

And Finally
5- Is Eulerian model able to predict the interface of water and air or the VOF model is the single model for this target?
Best Pleasure,

In this case wall boudary with zero shear stress can be used to simulate free surface. As to the Eulerian multiphase model I am not familiar with it.