## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### How to set up atmospheric pressure boundary condition ?

• ssr46
Subscriber

In Ansys CFX

I have two outlets at atmospheric exits and I want to add the boundary condition to it.

I'm confused with static/total/reference pressure boundary condition.

Any tips on this will do!

• raul.raghav
Subscriber

Can you provide a schematic of your model?

You can use a 0 Pa static pressure for outlets. If you define a surface as an "Outlet", the flow will not be allowed to enter the domain from that surface. If you are unsure about the direction of flow at the surface, you can define it as an "Opening", which acts like an Outlet if the flow is leaving the domain and if the flow enters the domain, the pressure is taken as total pressure and the static pressure is calculated from it. The following resources might be helpful to you:

• ssr46
Subscriber

Yes!  I use "opening" as the exit. "Outlet" boundary creates a wall and the solution fails.

How do I check in CFX-post about the pressure set to atmospheric at both outlets?

Also, I've attached the schematic of my model.

• raul.raghav
Subscriber

So there is no inlet in your fluid domain? Can you briefly describe what you are trying to model? Is it like a tank with a fluid present in it and it's getting discharged to the atmosphere?

In "CFX Solver" you can save a backup file while the simulation starts and during the solution process. Open CFD-Post and plot the contours at "outlet_1" and "outlet_2" to check the pressure at each of the outlets. Is this what you are trying to check?

• Raef.Kobeissi
Subscriber

Setting up 2 outlets as (Outlet Pressure) and assigning a pressure "0" on both should be sufficient to model your case with 2 outlets at atmospheric pressure as long as your reference pressure is 101 KPa.  the "0"  Pa pressure is a gauge pressure which is equivalent to 101 KPa absolute pressure. you can use CFD Post to check and verify the pressure using the function calculator as shown below:

• ballisticme
Subscriber

Hello All,

I am simulating a porous media and need to impose a confining pressure on the walls to the fluid domain but been struggling. Please, can anybody suggest ways to do this with either fluent or CFX. the schematic is shown below.

Thanks,

Yaqub

• sachin.kumar
Subscriber
You just give the pressure outlet boundary condition for both the outlets and keep the gauge pressure zero but make sure that the operating pressure is atmospheric which is a default in fluent
• DrAmine
Ansys Employee