# Discussion Forum

## Thermal expansion of a liquid

 Topics: Heat Transfer, Physics, Geometry
RSS feed   |   Turn on email notifications   |   5 Replies   Last post: March 3, 2013 2:09pm UTC

Matthew Malkin

February 19, 2013 9:15pm UTC

Thermal expansion of a liquid

Hi all,

I’m am trying to produce a model of a fluid enclosed on all sides except one by fixed constraints(walls), on the remaining face a thin diaphragm is in contact with the fluid. As such this is a closed system with no flow.

I would like to model the deflection and stress of the diaphragm wrt the temperature of the enclosed fluid. Clearly as temp increases thermal expansion will deform the diaphragm

I have tried to model the situation using the fluid-structure interface option on 4.2 however I can’t find a tutorial that features a stationary fluid?

Which interface should I be using?

Any help would be greatly appreciated!

Thanks,
Matt

Yevgeniy Davletshin

February 19, 2013 9:59pm UTC in response to Matthew Malkin

Re: Thermal expansion of a liquid

I'm not sure but my guess is that you want to include Heat transfer in your simulations with constant heat source, then in Fluid-Structural interaction you can add from Solid-Mechanics domain -> Linear Elastic Material -> Thermal Expansion.

Ivar Kjelberg

February 20, 2013 6:48am UTC in response to Yevgeniy Davletshin

Re: Thermal expansion of a liquid

Hi

For the solid you can add the thermal expansion, but if your fluid is static in a closed volume you cannot add the "thermal expansion" on the fluid in FSI.

So far I "cheat" usually using only "solid" and define my fluid as a "Linear elastic material" with nu Poisson = 0.49 and E = 1/3 of bulk modulus. Adding in the Nearly incompressible material, to solve also for "p" helps sometimes

But I would appreciate to have a better way, but I'm not sure which domain physics to use under "solid" to correctly model a fluid material of nu=0.5 for thermal expansion (in static approximation, no convective flow, typically for closed volumes filled with a fluid, in a solid enclosure, under thermal load)

suggestions appreciated

--
Good luck
Ivar

Matthew Malkin

February 21, 2013 11:13am UTC in response to Ivar Kjelberg

Re: Thermal expansion of a liquid

Thanks for the replies,

Unfortunately I am still having some problems.

I want to run the model at different temperatures however I am not interested in heat transfer within the model etc

Ivar,

To clarify you are suggesting using the fsi module and then defining both the liquid and solid domain as linear elastic materials? in this case there are no domains in fluid properties.

When I attempt this I get a generic error message regarding geometry and domains.

So far my model (attached) is extremely simple compromising of two domains (solid and liquid) in contact. when I am finalising the geometry should I form a union or a contact pair?

Is there a module I can use to model this other than fsi if I am effectively treating both domains as a solid?

Again sorry for the questions but I am struggling to get my head around this.

Thanks
Matt

Matthew Malkin

February 25, 2013 3:52pm UTC in response to Matthew Malkin

Re: Thermal expansion of a liquid

Any idea's?

Im pretty stuck on this one

Ivar Kjelberg

March 3, 2013 2:09pm UTC in response to Matthew Malkin

Re: Thermal expansion of a liquid

Hi

1) in FSI do not use assembly mode, so you get a continuity (in no way a "contact link) between Fluid and Structure
2) in FSI you have no thermal expansion node for the fluid so it will not work like that
3) my proposal was to use all "solid" but this assumes that the fluid is not "flowing" freely, but behaving as a "gelly" incompressible

--
Good luck
Ivar

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