# does the time step depend on constant source term?

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 18, 2011, 08:12 does the time step depend on constant source term? #1 Member   Shenren Xu Join Date: Jan 2011 Location: London, U.K. Posts: 63 Rep Power: 8 In 3D Euler FVM steady flow solver, the time step for local time stepping acceleration is scaled as (1) cell_volume /( lambda1+lambda2+lambda3) where lambda1,2,3 are spectral radii of the convective matrix. I do understand how formula (1) is derived. My question is, if there's a (constant) source term on the R.H.S. of the Euler equation, i.e., Original: du/dt + Flux(u)=0 Now: du/dt + Flux(u)=Constant then, will this constant on the R.H.S. change the time step? Can I still use formula (1) or should I formulate another time step to take into account the effect of the R.H.S term? Thanks.

 April 18, 2011, 10:04 #2 Member   Ramesh K Join Date: Dec 2009 Location: Bangalore Posts: 65 Rep Power: 9 Hi We know that CFL = (|U|*del_t)/delx, from which we get del_t = cfl*delx/IU| which can be written for 3D as delt = cfl * cell_volume / (|V.S|+c*|S|) . where S is the surface area vector. If the constant you were referring to is the artificial dissipation terms then the time step doesnot depend on those terms. If I am wrong please correct me. Thank you

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post zwdi FLUENT 13 December 5, 2013 18:58 nileshjrane OpenFOAM Running, Solving & CFD 4 February 25, 2013 05:13 Greg Givogue OpenFOAM Programming & Development 3 March 4, 2011 18:18 Martin Main CFD Forum 2 June 6, 2008 03:38 msrinath80 OpenFOAM Running, Solving & CFD 2 November 7, 2006 16:15

All times are GMT -4. The time now is 18:43.