[Nek5000-users] IFCHAR option in rea file

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

Dear NN,


If your flow is turbulent the answer is definitely Yes (they will be different) because of the standard sensitivity to initial condition concerns.


Despite this, both schemes are O(dt^k) accurate, meaning  that as dt-->0, the error goes to _zero_ as dt^k, where k=Torder is the prescribed temporal order.   Since the error goes to zero, both will deliver the same answer provided that the physical solution is stable and has an attractor.   [Understanding when such conditions prevail is often a challenge.]


Paul


________________________________
From: Nek5000-users <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: Monday, November 6, 2017 6:13:11 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] IFCHAR option in rea file

Hello,

  I have been using IFCHAR = TRUE in my simulations. The CFL number is
around
1.2 and the computations appear to go on nicely. I would like to know
if the flow field computed using IFCHAR=TRUE option is different than the
one obtained with IFCHAR=FALSE (albeit with smaller dt)? If yes, can the
difference
be significant?

Many thanks,
NN

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