<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div>Dear Emily<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>How much is the amplitude of your initial perturbation? if it is smaller than 10-3, it is unlikely from the nonlinear effect.<br></div><div><br data-mce-bogus="1"></div><div>I don't know how you solve OS equation, but the Reynold's number in OS equation is generally based on central line velocity. While the Reynold's number in Nek for the channel flow is generally based on mean flow velocity.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>If the wave was distorted, maybe you should check the shape of the disturbance, and the streamwise wave number alpha (which determines the length of computational domain.)<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Another reminder is that you need to run this case in temporal mode of OS equation if you use periodic boundary condition.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div data-marker="__SIG_PRE__"><div>Bien cordialement<br></div><div><br></div><div>Zhenrong JING<br></div><div><br></div><div>Doctorant (Doctor Candidate)<br></div><div><br></div><div>LHEEA</div><div><br></div><div>Ecole Centrale de Nantes<br></div><div><br></div><div><span class="_Xbe">1 Rue de la Noë, 44321 Nantes, France<br></span></div></div></div></body></html>