[Nek5000-users] Variable density flows

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

I may have misunderstood your Q
Did you mean that c initially has a max = 1 and that mixing will only cause it to go down? 
In this case check mass conservation
And make sure the initial density is accurately specified and that it gets updated correctly
Ammar

Sent from my iPhone

> On Oct 13, 2013, at 9:01 AM, nek5000-users at lists.mcs.anl.gov wrote:
> 
> I am not sure that what you are solving for  c  is a normalized scalar like a mass fraction Y for example 
> If c is not normalized May be the formulation is equivalent to
> C= rho* Y where y is a normalized scalar and rho is the total density..
> 
> Finally check mass conservation
> By integrating over the volume of the channel, the density equation
> d/dt integral(rho) + integral (u. Grad rho) =error 
> And see how error changes over time
> 
> Ammar
> 
> Sent from my iPhone
> 
>> On Oct 13, 2013, at 1:46 AM, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>> 
>>> On Sun, Oct 13, 2013 at 10:35 AM, <nek5000-users at lists.mcs.anl.gov> wrote:
>>> You can also try error function like profile with 0 value at the inlet and increases to a peak somewhere and stays constant up to the exit so gradient is0 at the exit
>>> Insulation normally refers to the diffusive flux (first form)
>>> Ammar
>> 
>> Thanks for the tips. I am using a smoothed initial condition for scalar now. However after some time the scalar does not stay within [0,1] which is important. My time step is already small with cfl ~= 0.1. What can I do to get better behaviour of the scalar ?
>> 
>> The diffusion coefficient for my scalar is quite small, D = 5*10^(-5).
>> 
>> Regards
>> praveen
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