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#21 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Here are some pictures to explain the different named selections that I've created (I've decided to hide some parts for each named selection, in order to be clearer in the visualization).
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#22 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
does it mean, that you've created real wall of syringe? (shape of water body and shape of syringe wall is different)
show cross section. zones air and water should have the same material, syringe wall has different material. between air and water there should be some boundary (tip of syringe) with interior boundary condition explain again, what problem do you have now best regards |
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#23 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hi,
Yeah, as I explained you I have sketched my syringe in 3D (with the tip), but it is hollow, so I used the "Fill" tool to create of volume in it. I've found a solution for my previous issue (air being considered as a solid), but when I display results I still have very weird things. Nothing seems to come out of the syringe into the cube of air ![]() I've added a boundary condition on the lower surface of the volume of fluid inside the syringe (check pictures), and it is an interior in the boundary conditions. However, I have the exact same results than when I didn't have it... By the way, as you can see on pictures, the lower surface of the volume of fluid is also the bottom of the hole of the cube of air. Thus, I really don't understand why it doesn't work, because this means that the surface at the bottom of the cube of air and the surface at the bottom of the volume of fluid are actually the SAME, so if it is defined as an interior, I don't understand why the fluid would be blocked. I am actually so lost ![]() ![]() ![]() I put you again in the pictures some details of the interface between air and syringe. To summarize, I've defined a named selection for the walls of the syringe, and another one for the walls of the air but only on the faces of the cube, not into the hole as you can see on the picture (because I already put walls on the tip in there). I just tried to put walls_air also in the hole (except on surface_tip), still same results! I try to be as clear as possible sorry.. I've enclosed a picture showing the complete list of my boundary conditions, if you see something weird tell me (surface_tip is an interior). I am actually quite desperate right now haha In my next message I will show you some pictures of my results. If you want I can directly send you my work if you give me your email. I guess it would be easier for you to understand and visualize. Anyway thank you so much for your time, actually I am in a research group and absolutely nobody here is able to help me on simulations, so you're kind of my only hope. ![]() Yoann |
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#24 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Here are some pictures of the (weird) results. It's like the fluid was under pressure at the top of the syringe, "stable" in it, and compressed against a wall at the bottom (nothing is going in the cube of air). Whatever the velocity inlet and the time step that I choose, I always face this problem.
Yoann |
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#25 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
in boundary conditions go to surface_tip and change type from wall to interior
make sure you have air material in syringe and air zones best regards |
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#26 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hi,
As I told you, surface_tip is already an interior... ![]() And I did a multiphase model, like in 2D: water in the syringe and air in the cube below. Why put air in both ? The goal of my work is to see the behaviour of the fluid in the syringe (water here) when going into air. And I think this doesn't change the issue of fluid not going out of the syringe. Do you have other solutions please? Thank you Yoann |
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#27 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
you should put air everywhere, but in syringe you put water later, after INITIALIZATION using PATCH tool
best regards |
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#28 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Actually it's already what I've done...
Do you have any other ideas to solve the issue at the interface? ![]() Yoann |
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#29 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
upload you case here
best regards |
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#30 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
I can't upload it here, I need your email address. Send me it by private message if you want
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#31 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hey,
I post here again because I really can't find any solution for my problem... I decided to slice everything in half to have a better visualization. However, I have a really weird a problem at the end of the tip (at the interface; oh what a surprise ![]() Can someone help me please ? ![]() ![]() ![]() Yoann |
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#32 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Here are pictures of the geometry + named selections.
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#33 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
And more details for the named selections.
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#34 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
switch off node values, when you plot contours
your pictures of results are confusing, just several rectangular regarding your model, because you've created real wall of syringe -> now you may delete surface on the tip called surface_tip. You can do it if you give the same material (air) for both zones body_air and body_fluid interior boundary will be created automatically (but it would be better if you check this) best regards |
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#35 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hey,
Thank for your quick reply again! ![]() I don't really know what to change here... I tried with "Steady" and "Transient", I have close results. Maybe the mesh is responsible for the issue at the end of the tip? Do you have some ideas please? Thanks again!! ![]() Yoann |
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#36 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
check you boundary conditions, in "inlet" boundary you should define water as fluid
best regards |
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#37 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hi,
Indeed it was a mistake from me! I had a volume fraction of 0 for water in the inlet, instead of 1... Thanks a lot for thinking about that! However I still have the issue at the end of the tip ![]() ![]() ![]() ![]() Thanks. Yoann |
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#38 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
use pressure inlet boundary condition in "inlet" not velocity inlet, vary pressure
best regards |
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#39 |
Member
Yoann Di Maiolo
Join Date: Jun 2019
Posts: 43
Rep Power: 7 ![]() |
Hi,
I've changed for pressure-inlet, but I'm not really sure which values I should put here (check picture). For a default Operating Condition (around 100000 Pa) and a Specified Operating Density of 0kg/m3, I've chosen a Gauge Total Pressure of 0Pa and an Initial Gauge Pressure of 0Pa as well. I've also tried an Operating Condition of 0Pa, a Gauge Total Pressure of 100000Pa and an Initial Gauge Pressure of 0Pa. In both cases, I have the same issue, just a small quantity of water going out of the syringe and air going up in the syringe... It's really like if air was trying to resist, this is so weird ![]() I also see during the iterations the following messages: reversed flow in xx faces on pressure-inlet 15, and this number is not going down, just fluctuating. Maybe I've defined my values for the inlet wrong? Thank you. Yoann |
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#40 |
Senior Member
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34 ![]() ![]() |
use Operating Condition of 0Pa (it doesn't matter)
Gauge Total Pressure of 500000Pa and an Initial Gauge Pressure of 0Pa switch off Specified Operating Density reversed flow in inlet is not normal. Play with time step size best regards |
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