<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>Hi,</div><div>I haven' t tried this myself, but I guess you could write a subroutine that calculates the maximum timestep from the scalar field and sets dt accordingly. Then simple call the routine from userchk.</div><div><br></div><div>Best,</div><div>Jan</div><div><br>Am 12.06.2017 um 18:15 schrieb <a href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a>:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html charset=us-ascii">Dear Neks<div class=""><br class=""></div><div class="">I am running a simulation of a channel, with a passive scalar. Using diffusivity=viscosity, the velocity field converges nicely, whereas the passive scalar blows up at some random point down the simulation. Reynolds number is 10 000 so its in the turbulent regime.</div><div class=""><br class=""></div><div class="">I suspect this is due to the fact that the passive scalar is intermittent, so sometimes large fluctuations will occur, totally uncorrelated to velocity fluctuations. to avoid the code to blow up, one would need to setup the timestep based on a courant criterion for the scalar, and not for the velocity. </div><div class=""><br class=""></div><div class="">has this already been implemented ?</div><div class="">or how do people avoid this ?</div><div class=""><br class=""></div><div class="">any suggestion is more than welcome.</div><div class="">thanks</div><div class="">Agnese</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Agnese Seminara</div><div class=""><div class="">--------------------------------</div><div class="">CNRS</div><div class="">Institut de Physique de Nice</div><div class="">Parc Valrose </div><div class="">avenue J Vallot</div><div class="">06108 Nice, France</div><div class=""><span style="color: rgb(38, 48, 51); font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);" class="">+33 (0) 492 076 775</span></div><div class=""><a href="http://sites.unice.fr/site/aseminara/" class="">http://sites.unice.fr/site/aseminara/</a></div></div></div></div></div>
</div>
<br class=""></div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>Nek5000-users mailing list</span><br><span><a href="mailto:Nek5000-users@lists.mcs.anl.gov">Nek5000-users@lists.mcs.anl.gov</a></span><br><span><a href="https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users">https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users</a></span><br></div></blockquote></body></html>