[Nek5000-users] Add a forcing term on scalar equation

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

Hi Iman,

I don't know what type of system you are trying solve but I want to
draw your attention on the following option:

You can use the PnPn formulation. First, a non-linear coupled scalar
system is solved using CVODE (a stiffly stable integrator).Then, the
hydrodynamic equations (velocity and pressure) are solved. The two
system are decoupled using a high-order splitting approach. We do the
same for chemically reactive flows.

Cheers,
Stefan


On 1/20/12, nek5000-users at lists.mcs.anl.gov
<nek5000-users at lists.mcs.anl.gov> wrote:
>
> Hi Iman,
>
> There are some minor bookkeeping issues here...
>
> Just to make certain we're on the same page, are you currently
> using Pn-Pn-2, or Pn-Pn ?
>
> Paul
>
>
> On Fri, 20 Jan 2012, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Paul,
>>
>> Numerically the momentum equation has an explicit forcing term.
>> Only that, it is based on the T at the same time. However, I would like to
>> first solve the equation for the scalar.
>>
>> In other words, I want to first solve the equation for T, use it to
>> calculate f(T) and afterward solve the momentum equation ( u_t=NS + f(T)
>> ). So How I can do that!?
>>
>>
>> Iman
>>
>>
>>
>>
>>
>> ________________________________________
>> 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: Friday, January 20, 2012 2:25 PM
>> To: nek5000-users at lists.mcs.anl.gov
>> Subject: Re: [Nek5000-users] Add a forcing term on scalar equation
>>
>> Iman,
>>
>> These can be coupled explicitly, but not implicitly.   Usually, however,
>> this is sufficent.  Equation are of the form:
>>
>>    u_t = NS +  f(u,T)
>>
>>    T_t = energy eq. + q(u,T)
>>
>> f & q explicit.   The code will take care of the bookkeeping.
>>
>> Paul
>>
>>
>> On Fri, 20 Jan 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>
>>> Thanks.
>>> So I just used the "USERQ" to implement the forcing term to scalar filed
>>> explicitly.
>>>
>>> In the next step, I want to coupled the scalar field to Navier-Stokes
>>> equation using a forcing term.
>>> In this case, the forcing term is a function of scalar field and I would
>>> like to implement it implicitly.
>>> As far as I know, if I used USERF, the scheme is explicit. So how can I
>>> add a forcing term to N-S equation implicitly!?
>>>
>>> Iman
>>>
>>>
>>>
>>> ________________________________________
>>> 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: Thursday, January 19, 2012 4:20 PM
>>> To: nek5000-users at lists.mcs.anl.gov
>>> Subject: Re: [Nek5000-users] Add a forcing term on scalar equation
>>>
>>> It's actually evaluated explicitly, so you shold be ok.
>>>
>>> Paul
>>>
>>>
>>> On Thu, 19 Jan 2012, nek5000-users at lists.mcs.anl.gov wrote:
>>>
>>>> Hi
>>>>
>>>> I would like to add a forcing term to the scalar equation.
>>>> According to the Nekton manual, Chapter 5, the forcing term is treated
>>>> implicitly and the convective term is integrated using the third order
>>>> Adam_Bashforth scheme (AB3).
>>>> For my case, the forcing term is a nonlinear function of the scalar
>>>> field, so I cannot use the implicit scheme and I should lump it with the
>>>> AB3.
>>>> Therefore, could you please guide me and indicate where in the code I
>>>> can find the implementation of AB3 for the convective term of passive
>>>> scalar?
>>>>
>>>> Cheers
>>>> Iman
>>>>
>>>>
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