Airflow Direction Question

I am wondering why the airflow in my model loops back around at the end of the flow region. I set the left side of the flow region to a velocity inlet and the right side to pressure outlet, so the air should just pass through the model.

Also does the size of the flow region effect the temperature of model? I made a smaller flow region model with the same attributes as the larger model and surprisingly my internal temperatures were different. What would be the reason behind this?

Hi Kyle!

Would it be possible to also include the link to the project, please?

Best regards,
Fillia

https://www.simscale.com/workbench/?pid=7008745691320633198&rru=465ad0d3-d784-4df6-9ce2-14e8558d870e&ci=cfbae570-6ccb-4f81-8adf-a3b6e8eb8c76&ct=SOLUTION_FIELD&mt=SIMULATION_RESULT

Hi,

To me this looks like a boundary condition effect. The inlet has an almost stale breeze (0.2 in/s), and we have a no-slip wall on the top. This basically represents a hut inside a physical wind tunnel.

I’d normally expect a “Natural convection inlet/outlet” boundary condition to the top, sides, and the outlet of the domain. Only the ground would be a no-slip wall.

1 Like

Would I still apply a pressure outlet at the end of the flow region? And do you know why the internal hut temperatures are different according to the size of the flow region?

There are too many simulation trees/runs in the project, so it’s difficult to tell. And the “outlet” could be either pressure outlet or natural convection inlet/outlet.

Just as a side note (and this is something that I mentioned before), it’s important to have a domain with a reasonable size, to make sure that the boundaries are not playing a role in the results of the regions of interest.

This is one from June 4th, indicating the need to extend the boundaries of the domain:

1 Like

I made the adjustments you recommended and this was the result… the air is coming from the left but the vectors are ventilating upward? I circled which simulation and test run this is associated with.

Hello,

A couple of things:

  • The velocity is so small right now through the inlet (~0.0002 inches per second) that it probably won’t even be noticeable.

  • The fluid enters the domain at 60 F (~15 ºC) while the ground’s temperature is fixed at 25 ºC. As you would expect, you are seeing these convection patterns all over the place :slight_smile:

I changed my flow rate from (0.1 in^2/s) to (176 in^2/s) from last time we talked. Is (176 In^2/s) still to small? Or do I need to change a different factor?

Well, the velocity would be calculated with flow rate divided by the area of the inlet.

By eyeballing the inlet dimensions, we have something around 1200 inches by 700 inches. If you do the math, you will obtain the inlet velocity.

Again, I can’t answer this question for you, but I can say that with a velocity of 0.0002 inches per second, you will hardly see any flow from the inlet reaching the other side of the domain. The convection from the hut would give you velocities much larger than that.