topic Re: Natural Convection velocity plot in CFD Forum

Natural Convection velocity plot

Anonymous — Fri, 17 Aug 2018 05:06:43 GMT

Most of the time we get this kind of velocity profile. Is this correct? Region Box is created with local mesh, NAR<100, ke Model, p=0 @ top & bottom.

Re: Natural Convection velocity plot

Jon.Wilde — Fri, 17 Aug 2018 05:35:45 GMT

Looks pretty good to me, it is surely what you would expect right?

Re: Natural Convection velocity plot

Anonymous — Tue, 21 Aug 2018 04:04:37 GMT

I was wondering if this standard configuration for buoyancy analysis is accelerating the velocity profile or not.

When buoyant rising fluid exit the top domain, solver automatically balances mass with the inlet where fluid enters from the bottom at a certain speed. This globally uprising airflow is inevitably accelerating the buoyant profile by entrainment/viscosity, isn't it?

Re: Natural Convection velocity plot

Jon.Wilde — Tue, 21 Aug 2018 06:09:57 GMT

This is why we have a pretty large domain, so it should be negligible.

In reality, the rising plume would also generate a flow over the unit, right?

Re: Natural Convection velocity plot

Anonymous — Tue, 21 Aug 2018 06:18:22 GMT

Yes its above enclosure. But we have very large domain compared to enclosure. More than 10 times and with box region.

Temperature flow is ok, is this velocity profile acceptable?

Re: Natural Convection velocity plot

Anonymous — Tue, 21 Aug 2018 06:41:13 GMT

True, I just had a doubt here. Thank you

Re: Natural Convection velocity plot

Jon.Wilde — Tue, 21 Aug 2018 07:03:47 GMT

What I can say from experience is that I have had some very accurate results using both the 'chimney' and 'bucket' approaches 🙂

Do always visit here to ask if you are ever in doubt with a simulation.

Hope that helps!

Re: Natural Convection velocity plot

Anonymous — Tue, 21 Aug 2018 07:14:22 GMT

Chimney means adding box region with localized mesh on top on enclosure right...

What is bucket ?

Re: Natural Convection velocity plot

Anonymous — Tue, 21 Aug 2018 08:48:49 GMT

Hi,

I think Jon is referring to the User's guide here:

http://help.autodesk.com/view/SCDSE/2019/ENU/?guid=GUID-E0609A21-541D-4D11-9663-93476E26CF8F

Extract:

Table-Mounted

Model a device mounted on a horizontal surface. An example is a router on a table. (This is sometimes called the "bucket" configuration.)

Air-Mounted

Model a device mounted far from physical boundaries, such as on a pole or from a wire. An example is a telecommunications module suspended from a utility line. (This is sometimes called the "chimney" configuration.)

Re: Natural Convection velocity plot

Jon.Wilde — Tue, 21 Aug 2018 09:16:15 GMT

Very kind @Anonymous, glad you are here to help 🙂
Thank you!