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#1 |
New Member
Kim Gunhyeong
Join Date: May 2018
Location: Seoul, Korea
Posts: 9
Rep Power: 8 ![]() |
Hello
![]() I made transient pipe model as below ■ Type - Transient(Total time 1s, Timestep 0.01s) ■ Fluid model - 2 Fluid pair model(air and water) ■ Boundary condtion - 1 inlet(opening, cart vel 1m/s, Xwater=0.8/Xair=0.2) - 1 outlet(opening, opening pres. and dirn 0 Pa) - 1 conditional connection(pressure condition) at middle point. ■ Initial condtion : 0 Pa, 0 m/s and Xair=1 But when I start solver, it is stopped by overflow at FIRST step. Please help me ); |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
Are the fluids incompressible? You have a velocity inlet, so if you block off the connection the solver will crash as you have said fluid must go in but given it nowhere to go.
You have to be careful with the conditional opening condition that the open and closed conditions are physically realistic. Also, note that opening and closing is also very numerically aggressive and if your simulation is unstable it could trigger divergence and crashing.
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#3 | |
New Member
Kim Gunhyeong
Join Date: May 2018
Location: Seoul, Korea
Posts: 9
Rep Power: 8 ![]() |
Quote:
And I turn off conditional connection option, but it doesnt work. It works in static state, so maybe tranisent setting problem? |
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#4 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
The fluids you chose are incompressible. So my comment is correct, when your condition condition closes the solver will crash.
If you say it crashes when you turn the conditional condition off then something else is also happening. Please post your output file and an image of what you are modelling defining where the boundary conditions are.
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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Tags |
conditional open state, multi phase flow, opening boundary, transient analysis |
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