[Nek5000-users] gmers solver issue

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

Hi Dante,


A few questions -


Do you have the pressure projection turned on? (p93-95)


What is your iteration tolerance (p22, divergence) ?


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: Wednesday, May 16, 2018 3:34:42 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] gmers solver issue


Hello,



I trying to run the DNS of a pipe-like configuration with NEK-5000  but I’m facing some issues that I cannot fully understand.



More specifically, I am using the PN-PN formulation and the simulation slows down drastically after certain time. I have observed that when

this  happens the number of GMRES iteration for the pressure solver increases (from 50 at the beginning of the simulation to 170)

and the norm of the divergence of the velocity increases and I get a WARNING DIV(V)-QTL to large (~ 1.2E-1).



The problem appeared initially using a 3rd order polynomial, but even using higher order (9 th) does not solve the issue.



Do you have some hints about the nature of this issue?





Kind regards,

Dante


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