[Nek5000-users] conj. ht. transfer

[nek5000-users at lists.mcs.anl.gov]

Dear Paul and Stefan,

thanks a lot for your help.
Sorry for the late reply. I checked many times and I have always obtained the same result. The heat fluxes match very well for equal vtrans but they don't for different vtrans. I think that from a physical point of view the fluxes have to match always.
Stefan, I'll send you the case with an e-mail.

Thanks again.

Regards,
Andrea.
________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Sunday, October 16, 2011 6:01 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] conj. ht. transfer

Can you post the code you have used to validate the interface condition?
Stefan

On 10/16/11, S K <stgeke at googlemail.com> wrote:
> Andrea,
>
> Let's start with an important note: The implement SEM is locally not
> conservative. Thus, the fluxes do not need to match. However, it would
> be suspicious if the flux conservation at the interface is
> proportional to something!
>
> I'll have a look at it.
> Stefan
>
> On 10/16/11, S K <stgeke at googlemail.com> wrote:
>> Hmm, that puts some pressure on me. Investigation starts now :)
>> Cheers,
>> Stefan
>>
>> On 10/16/11, nek5000-users at lists.mcs.anl.gov
>> <nek5000-users at lists.mcs.anl.gov> wrote:
>>>
>>> Dear Andrea,
>>>
>>> Thank you for your careful investigation of this issue.
>>> We'll dig into it in the next 36 hours and hopefully we
>>> will get the problem resolved quickly.
>>>
>>> Best regards,
>>>
>>> Paul
>>>
>>>
>>>
>>>
>>> On Sun, 16 Oct 2011, nek5000-users at lists.mcs.anl.gov wrote:
>>>
>>>> Dear all,
>>>>
>>>> I was running a simple case with conjugate heat transfer. I managed to
>>>> validate it against some analytic data.  I checked whether the heat
>>>> fluxes
>>>> at
>>>> the interface between solid and fluid match or not. For any ratio of
>>>> solid
>>>> conductivity over fluid conductivity they match very well especially if
>>>> the
>>>> grid is very refined at the interface. The problem is that they match
>>>> only
>>>> if
>>>> vtrans of solid is the same as vtrans of the fluid, else the ratio of
>>>> the
>>>> two
>>>> fluxes is proportional to the ratio of vtrans, which is wrong.  I had a
>>>> look
>>>> into the code even though I am not very expert. I am using cvode. In
>>>> fcvfun
>>>> there is a call to makeq. In makeq, after the call to wlaplacian and
>>>> add2,
>>>> the rhs, which is bq, is divided by vtrans. When we are back to fcvfun,
>>>> there
>>>> is a call to dssum over ydot. I am not sure but I think that dssum
>>>> mixes
>>>> the
>>>> properties of fluid and solid, therefore the transient equation which
>>>> is
>>>> solved for the temperature at the interface has a flux which is divided
>>>> by
>>>> vtrans of the fluid and another flux which is divided by vtrans of the
>>>> solid,
>>>> therefore the two fluxes can not match at the interface unless solid
>>>> and
>>>> fluid have the same vtrans.  If this is really the problem, I think it
>>>> could
>>>> be solved by dividing bq at the interface by vtrans of the solid only,
>>>> before
>>>> dssum is performed.  I'll check again my case to be sure that what I
>>>> observed
>>>> was not due to an error.
>>>>
>>>> Thanks in advance for your help.
>>>>
>>>> Regards, Andrea.  _______________________________________________
>>>> Nek5000-users mailing list Nek5000-users at lists.mcs.anl.gov
>>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>>>
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>>
>
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