 ## Fluids

• DetroitKiddo
Subscriber

Hello all,

I have a question relating to scaling up an inlet boundary condition. I have two models I am trying to simulate with different inlet areas which I will explain in detail to clarify my question.

My first model has an inlet area of 602 mm^2 with a inlet velocity of 0.00000968992248 m/s.

My second model has an inlet area of 402 mm^2. My goal is to scale up model 2's inlet to the the same inlet velocity as the 602 mm^2 inlet. Basically with my second model due to CAD restrictions my inlet size is stuck at 402 mm^2. I cannot increase it to match model 1. So since I cannot scale the dimensional size I would like input a velocity that would give me the same velocity/area as model 1 so they are equal. Is this possible in ansys with a simple ratio formula ? Is there a way to calculate this new velocity so they both match and account for the scale up ?

Thank you all for the help!

• SRP
Subscriber

Hi,

Reynolds number can remain constant in both scenarios. After that, try to determine the velocity for the second scenario.

Thank you

• DetroitKiddo
Subscriber

Hello SRP,

I checked the velocity being produced for the second model and it is different so I am not sure how to assign the correct velocity value to match the output correct if you can clarify that part from your reply. Thank you

• Rob
Ansys Employee

Are you trying to match mass flow? Or velocity?

• DetroitKiddo
Subscriber

Hello Rob,

I can match either one it does not matter on my end. The mass flow rate into the 602 mm^2 inlet area is 0.00000581 kg/s. If there is a way to scale it and match this same flow for the 402 mm^2 thats fine. Either mass flow or velocity both would be fine as long as I can scale it correct so both surface areas are producing the same inlet flow into the domain. Thank you for your reply Rob!

• Rob
Ansys Employee

Then why don't you scale by area? It's a relatively simple calculation on paper. If you're not sure, ask your Prof. 