Problems of numerical instability because of high gradients

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 LinkBack Thread Tools Display Modes
 September 15, 1998, 08:41 Problems of numerical instability because of high gradients #1 Xiangyang Ye Guest   Posts: n/a I use CFD in the development of high voltage circuit breaker. In this field, the fluid flow is transient, turbulent, compressible with Mach number from 0.2 to 5. Our CFD codes are of finite volume and time stepping methods. There are extremely large gradient of temperature from 300K to 20000K and large gradient of pressure from 1 bar to 100 bar. Therefore, we suffer the problem of numerical instability because of these extremely large gradients. We must often strongly reduce the time step, but then we get an extreme long calculation time. Are there any people who have experience to treat such problem and know robust schemes for the discretizations and for the artificial viscosity?

 September 22, 1998, 01:35 Re: Problems of numerical instability because of high gradients #2 Oleg Mikitchenko Guest   Posts: n/a As I understand your problem, I may offer two solutions First is to use regularizations schemes, for example Il'in scheme. Second is to use adaptive grids - grids with variable step. {calculate with constant step; while (solution is bad) { change your grid - condence in areas with large gradients in your solution(in bad sulution); recalculate on this grid; } }

 September 22, 1998, 04:07 Re: Problems of numerical instability because of high gradients #3 Xiangyang Ye Guest   Posts: n/a Thank you very much for your tips. Would you please recommend me the literature of the regularizations schemes you mentioned? X. Ye

 September 28, 1998, 01:27 Re: Problems of numerical instability because of high gradients #4 Oleg Mikitchenko Guest   Posts: n/a Here are two titles: 1.Uniform numerical methods for problems with initial and boundary layers / E.P.Doolan, J.J.H.Miller, W.H.A.Schilders (Dublin 1980) 2.Shear flow in surface oriented coordinates./Ernst Heinrich Hirschel, Wilhelm Kordula (Wiesbaden 1981-1986) At the first book you can find many references, and what about adaptive grids?

 September 28, 1998, 03:48 Re: Problems of numerical instability because of high gradients #5 Xiangyang Ye Guest   Posts: n/a Thank youu very much for your recommendation of literature. I will read them firstly. We do'nt have adaptive grids in our code, because for finite volume method this technique is not very convenient. But we will consider to use it. X. Ye

 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 igor Main CFD Forum 0 May 28, 2003 07:24 sreekanth Main CFD Forum 1 August 6, 2001 15:09 mehdi fteity Main CFD Forum 3 September 14, 2000 21:44 Jon Johnson Main CFD Forum 5 October 30, 1999 10:00 Eleuterio TORO Main CFD Forum 0 December 18, 1998 13:41

All times are GMT -4. The time now is 12:50.

 Contact Us - CFD Online - Privacy Statement - Top