topic Re: Effect of temperature on flow in CFD Forum

Effect of temperature on flow

Anonymous — Fri, 30 Jun 2017 16:42:37 GMT

I have a liquid flow in a pipe and i'm simulating it with Autodesk CFD.

When i set up a mass flow inlet, and pressure outlet i obtain a solution..

If I introduce also a temperature inlet condition the solution is different from the previous one (actually is the same at inlet and outlet, but different in the central part of the pipe - for example for the velocity). The fluid is incompressible, so is strange the difference of the solutions.

What do you think about this? Could it be right?

The mesh is very good (i've used also the adaptive mesh and i have at least 6 nodes in each gap)

Thank you

Re: Effect of temperature on flow

Jon.Wilde — Fri, 30 Jun 2017 20:57:02 GMT

Hey,

Might you share an image to explain what you mean by different?

You would expect the inlet to be different as the flow is undeveloped (which is why we usually have a long extension before the region of interest).

Thanks,

Jon

Re: Effect of temperature on flow

Anonymous — Fri, 30 Jun 2017 21:52:50 GMT

Thank you for your reply.
To be clear. I created two scenarios:
1 scenario: volume flux at inlet and pressure static gage at outlet (0 Pa)
2 scenario: volume flux at inlet + Temperature at inlet and pressure static gage at outlet.

Then i used the plot function to see the velocity magnitude in the two scenarios and i compared them in decision center.
The trend of velocities were different even if i expected similar trends because the flow is incompressible, and the Temperature should not affect the results. (Specifically, in the second scenario the velocity is higher in the central part of the pipe, while is very similar at inlet and outlet).

Maybe i don't have to introduce the Temperature because I'm not interested in heat generation bit just the flow. What do you suggest?

Information about the solver: turbulence model - K epsilon with ADV1 but i tried also with ADV5.

Fluid is water in a small pipe with some curvatures.

Thank you very much for your preciois help.

Re: Effect of temperature on flow

Jon.Wilde — Mon, 03 Jul 2017 08:02:32 GMT

How different?

Could you share an image of the results compared and also of the mesh?

Are you sure that temperature isn't having an effect? Are the fluid properties the same or are they changing with temperature? (This depends on how you set the model up...).

Thanks,

Jon