You have to use two scalars (+temperature) if your material properties (jet/air) differ. On 22 Jan 2018, at 10:57, "[email protected] <mailto:[email protected]> " <[email protected] <mailto:[email protected]> > wrote: The ideal gas law is not hard coded. You can chance the material properties through uservp() and the so called thermal divergence (Drho/Dt) in userqtl() in the usr file. On 21 Jan 2018, at 19:00, "[email protected] <mailto:[email protected]> " <[email protected] <mailto:[email protected]> > wrote: Hello All, I'm trying to simulate a low density jet expanding into air using low Mach number formulation. I have followed the steps for enabling the stress formulation from the documentation. Is it enough to specify the variation of viscosity with temperature (sutherland formula) in the .usr (in uservp() section) file? If yes, is there an example in Nek5000 repo? And it says in the Nek Documentation that Idea Gas equation ( P = rho*R*T) has been hard coded. So where do I input the information about R? And how will the solver know that bulk fluid is air and the incoming jet is a fluid with lower density? I'm really grateful to any help I can get regarding my question. Thanks in advance.  -- Nitish Kovalam Aerospace Engineering Indian Institute of Space Science and Technology _______________________________________________ Nek5000-users mailing list [email protected] <mailto:[email protected]> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users _______________________________________________ Nek5000-users mailing list [email protected] <mailto:[email protected]> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users