# How Do I Calculate the Velocity of the Flow That Is Sucked Into Two Parallel Walls by a Fast Moving Flow?

I'm trying to solve a problem where I calculate the velocity of the setup bellow. Basically I have two very long(basically infinite for calculation purposes) plates, and I have one central jet of gas that is moving very quickly(I'm currently simulating the velocity and mass flow rate of the gas). However, I'm trying to calculate the amount of gas, and the velocity that will be sucked in as a result of the fast moving flow. I know the distance between the two plates, as well as the distance between the source of the fast moving flow and the top two plates but I'm unable to calculate the velocity of the sucked in gas at the top of the two plates. Could someone help me solve this issue? Thank you

What you want is the mass flow rate out the top of the device, not "velocities sucked in." The velocity of the entrained air is irrelevant.

That said, this is a very complex problem. A few of the variables:

• pressure of air entering the jet
• Nozzle configuration and size
• all relevant dimensions
• wall materials

Once you have all that you can go and search for the general solution of mass flow rate at a distance from the nozzle. Then you would adjust based on the walls. I'm sure all this has been modeled so the work is finding a model you trust. I would consider this graduate-level fluids work.

• Doesn't answer the question, and you didn't mention the most important factors that govern the result. If they say they want the velocity sucked in, let's assume that's what they want. Commented Jun 13, 2021 at 10:16
• @PhilSweet, let's assume instead that "velocity being sucked in" isn't a thing. Commented Jun 13, 2021 at 19:53