## Fluids

#### Boundary Condition

Subscriber

I am doing a simulation where I want 60% of the flow to go through one outlet1 and rest 40% to go through another outlet2. Which boundary condition should I use? I am using outflow bc with 0.6 and 0.4 flow weightage to each outlets but after looking into the streamlines flow doesnot pass through outlet1. What should I do to make it correct?

• SRP
Subscriber

Hi,

I assume you know overall flow rate. Using bernoulli you can calculate pressure at both the outlets. Now you can try velocity inlet bondary condition and pressure outlet boundary condition.

Hope this helps to solve problem.

Thank you

Saurabh

Subscriber

Hi SRP,

Could you please suggest me how to calculate the pressure at the outlets? I tried using mass flow boundary condition at inlet and both outlets but the residual didn't converge and the pressure value was -0.31 Pa. But I didn't think it will work. Is there any way I can do this?

• SRP
Subscriber

Hi,

It is not necessary to use mass flow inlets in incompressible flows because when density is constant, velocity inlet boundary conditions will fix the mass flow.

Outflow boundary condition used to model flow exits where the details of the flow velocity and pressure are not known prior to solution of the flow problem. They are appropriate where the exit flow is close to a fully developed condition, as the outflow boundary condition assumes a zero streamwise gradient for all flow variables except pressure.

For the calculation of pressure, try to apply bernoulli between two points. But I suggest try using velocity inlet and outflow boundary condition at exit.

Thanks

Saurabh

Subscriber

Hi Saurabh,

The outflow condition doesn't match with other experimental results. I think my geometry is small so the flow might not be fully developed. I tried using pressure outlet with targeted mass flow rate but it didn't work. I think there must be easier way to achieve targeted mass flow rate in ANSYS. This problem is quite trivial.

• SRP
Subscriber

Hi,

Can you please share screenshot of geometry?

Thanks

Saurabh