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-   -   divergence due to high pressure drop in two-stroke scavenging (http://www.cfd-online.com/Forums/fluent/117848-divergence-due-high-pressure-drop-two-stroke-scavenging.html)

renna.ale May 16, 2013 05:29

divergence due to high pressure drop in two-stroke scavenging
 
Hi,
I'm working about a model in fluent of two-stroke engine uniflow scavenging, with dynamic meshes of piston and exhaust valves. The start of my simulation is the exhaust valves opening (lift from 80 CAD to 250 CAD); near BDC, the piston opens 14 ports of intake (opened from 115 CAD to 245 CAD). I initialize my cell zones with exp. data, so I have high pressure and temperature in cylinder (18 bar, 1600 K) and lower conditions in intake volume and exhaust pipes (about 2.5 bar). This high pressure drop between the volumes makes the simulation crash/diverge at first 2 iterations. If I simulate the same model with lower pressure drop (e.g. 0.03 bar and not 15.5 bar!!!) there's no problem.
Can anybody help me?
Thanks.

fluent87 May 16, 2013 08:58

Hi,
do you try simple model calculation?

Good Luck!

venkateshaero May 16, 2013 09:52

u can slowly rise the pressure after convergence
0.03 to 0.1 similar like

renna.ale May 17, 2013 10:47

how can I do this?
Thx

venkateshaero May 17, 2013 15:13

Please send some figure to understand your problem....

slowly increases input values from low values


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