<div dir="ltr">Dear Vlad,<div>the low Mach Pn-Pn approach is based on the 1997 (JSC) and 1997 (JCP) papers you mention and it consists of 3 steps as you describe, i.e.:</div><div><span style="font-size:12.8px">a) first the velocity is updated using the extrapolated convective term, </span></div><div><span style="font-size:12.8px">b) then the Laplacian of pressure is calculated due to convection, after that </span></div><div><span style="font-size:12.8px">c) the velocity is updated using the pressure gradient and accounts for viscous term</span><br></div><div><div>The coupled Helmholtz solver is used for the velocities only when using ifstrs=true, that</div><div>is when you want to include the full stress tensor. Otherwise, it is using separate Helmholtz solves for each of the velocity components, similar to Pn-Pn-2. </div><div>Hope this helps clarify things.</div></div><div>All the best,</div><div>Ananias</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 6, 2017 at 7:29 AM, <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Neks,<br>
<br>
reading the documentation I got the impression that Pn-Pn solver (low Mach) first solves the pressure where the convective and viscous (!) terms are taken into account. After that using this p^{n+1} we solve for velocity field. It seems that the algorithm consists of only 2 steps (pressure + velocity).<br>
<br>
However, reading the paper by Tomboulides, Lee, Orszag (1996) which is referenced inside the code, I see the projection algorithm where first the velocity is updated using the extrapolated convective term, then the Laplacian of pressure is calculated due to convection, after that the velocity is updated using convection and pressure gradient. The last step accounts for viscous term.<br>
<br>
I am a bit confused, could you please help me out here? Which method is used?<br>
<br>
PS. Another thing is the coupled Helmholtz solver in Pn-Pn. I see that in case of Pn-Pn-2 each velocity component is treated separately (segregated solver). However, this coupled thing slightly confuses me, why not treating it separately as in Pn-Pn-2? Could you please comment there as well? Thank you.<br>
<br>
Best regards,<br>
Vlad<br>
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