## Fluids

#### Are there boundary conditions that is able to be used instead of periodic boundary condition?

• P_Heng
Subscriber

Hello everyone, have the awesome day.

I have some problems to ask all of you.

I got a research from my professor and the research is related to the fluid flowing across the domain under the ground.

I have to use the periodic boundary condition for my domain because This research involves the nature flow and I am allowed to add the gravity = 1, viscosity = 1, density = 1 (using boussinesq) only.

For my whole domain I can use the periodic boundary condition. And then, my professor wanted me to cut the domain into 4 sections and I can still use the periodic boundary condition because both interfaces are the same shapes.

The problem comes now when my professor wanted me to cut the domain into 8 sections and I cannot use the periodic boundary condition because both interfaces are not the same. I will send the pictures for all of you.

I want to know that are there boundary conditions that is able to be used instead of periodic boundary condition?

I also want to tell that the velocity result of whole domain and 1/4 domain are the same. But their results are different from 1/8 section of domain because I cannot use the periodic boundary condition for 1/8 and I try the other boundary condition, such as symmetry boundary condition.

Inside curves of the domain is solid.

• P_Heng
Subscriber
Hello everyone
I want to know that are there boundary conditions that is able to be used instead of periodic boundary condition for 1/8 sections domain?

My regards P. Heng.
• Rob
Ansys Employee
Given that gravity will act "up" and that the surfaces aren't periodic I don't know which boundary you can use as the results will be computationally correct but physically meaningless. However, with that mesh I'd not trust any results from the solver.
• P_Heng
Subscriber