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-   -   Segregated vs Coupled Solver (http://www.cfd-online.com/Forums/star-ccm/110685-segregated-vs-coupled-solver.html)

badger1 December 18, 2012 06:47

Segregated vs Coupled Solver
 
Hi,

If I am running a simulation should I be able to switch between these two solvers with little difference.

Currently I am trying to simulate a turbine blade and when I run the simulation in Segregated mode it runs fine (with constant density also) but when I change the solved to Coupled (with ideal gas) it no longer works and never converges and gives a really unstable solution that is continuously changing.

Does anyone know what I could be doing wrong?

Thanks

LuckyTran December 23, 2012 23:53

The coupled solver is generally more unstable. In terms of stability

constant density segregated > ideal gas segregated > ideal gas coupled

Quote:

Originally Posted by badger1 (Post 398050)
If I am running a simulation should I be able to switch between these two solvers with little difference.

In general, expect a difference. Especially if you are switching between constant density and ideal gas.

siara817 December 25, 2012 12:38

When you use coupled flow, the software uses coupled equations to solve pressure and velocity. This is proper when you have high density, or high Mach. It will use more CPU and it will converge slowly but the result will be more accurate. when you use the segregated, then the segregated equations. It is proper for standard case, when there is no complicated physical conditions. It uses less CPU and it will converge faster.


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