[Nek5000-users] time derivative

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

thank you.

i do have a follow up question.
My case is a DNS of a turbulent channel.
I was hoping to use the the characteristics method (IFCHAR=T.)
and a target CFL number of 1.5 - 2.0 .

To compute time derivatives I am using a normal finite difference 
[u(t)-u(t-dt)]/dt
but the results are suspicious.

Given the large time step, do you think it is possible to
Have reliable accelerations with this method?
Are there any better ways to compute them?

thank you a lot.
francesco




On 12/13/2010 04:59 PM, nek5000-users at lists.mcs.anl.gov wrote:
>
> Hi Francesco,
>
> Yes ... that should work.  Always a good idea to verify by
> storing your own on a test...   The number of values stored
> varies according to Torder, as I recall.
>
> Paul
>
> On Mon, 13 Dec 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
>> hi all,
>>
>> i need to compute time derivatives of the velocity.
>> Is VXLAG(:,:,:,:,1) the vx field of the previous time step?
>>
>> thank you
>> francesco
>>
>>
>>
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