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Mr.Ivar, could you check it for me again?
Posted Apr 11, 2011, 3:32 p.m. EDT Fluid & Heat, Mesh, Studies & Solvers, Structural Mechanics Version 3.5a, Version 4.1 2 Replies
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Hi Mr ivar,
According to your suggestions, I try to fix it and I still have something really confused!
This is the precious suggestions that you give to me!
there are many things here that I do not really catch, but I believe also it's because I do not fully understand your model, a few items I can suggest to check:
1) you could probably use the FSI module, as there all three physics are already combined
2) the inlet 1 you set up the velocity with an "s" but you have 3 segments, and s is redefined on each going from 0, to 1 along the edge, have you checked that the initial value velocity is already more or less as expected ?
3) I do not understand "inlet 2" this is a wall not an inlet ? I'm missing something ;)
4) boundary loads 1 and 3 of "0" do not bring anything
5) in the solid Mechanics do not leave an entry empty, add a "0" to the xref (even if you do not use it)
6) in the moving mesh, by default everything is fixed, I believe you should set a free deformation to the fluid part
7) your prescribed mesh displacement is not set you need to define something also for the boundaries
8) remove the not used solver cases and keep only one
9) try to solve only one physics at the time, to check that they are ok, you can also just get the initial conditions loaded to test those also
Here is my confusions:
About 2) the three segments in inlet 1 ,3,5 has the same conditions. Does I make some mistakes here?
3) inlet 2 , actually it is the inner boundary of the fluids, it has the same velocity as the inner boundary of the membrane.
4)boundary loads 1 and 3 , I want to do is they are like fixed, should I use the prescribed displacement? I check in the old version 3.5, it should use “standard notation" , Rx 0m Ry 0 m
7) prescribed mesh displacement is the membrane's mesh displacement, so I think it should be u2 and v2, is it right?
My model is about the single valve, the domain 4 8 9 13 15 is the solid membrane, when the flow enters from left to right, I need to find out how the membrane acts and how the fluids act.
Thank you so much!
According to your suggestions, I try to fix it and I still have something really confused!
This is the precious suggestions that you give to me!
there are many things here that I do not really catch, but I believe also it's because I do not fully understand your model, a few items I can suggest to check:
1) you could probably use the FSI module, as there all three physics are already combined
2) the inlet 1 you set up the velocity with an "s" but you have 3 segments, and s is redefined on each going from 0, to 1 along the edge, have you checked that the initial value velocity is already more or less as expected ?
3) I do not understand "inlet 2" this is a wall not an inlet ? I'm missing something ;)
4) boundary loads 1 and 3 of "0" do not bring anything
5) in the solid Mechanics do not leave an entry empty, add a "0" to the xref (even if you do not use it)
6) in the moving mesh, by default everything is fixed, I believe you should set a free deformation to the fluid part
7) your prescribed mesh displacement is not set you need to define something also for the boundaries
8) remove the not used solver cases and keep only one
9) try to solve only one physics at the time, to check that they are ok, you can also just get the initial conditions loaded to test those also
Here is my confusions:
About 2) the three segments in inlet 1 ,3,5 has the same conditions. Does I make some mistakes here?
3) inlet 2 , actually it is the inner boundary of the fluids, it has the same velocity as the inner boundary of the membrane.
4)boundary loads 1 and 3 , I want to do is they are like fixed, should I use the prescribed displacement? I check in the old version 3.5, it should use “standard notation" , Rx 0m Ry 0 m
7) prescribed mesh displacement is the membrane's mesh displacement, so I think it should be u2 and v2, is it right?
My model is about the single valve, the domain 4 8 9 13 15 is the solid membrane, when the flow enters from left to right, I need to find out how the membrane acts and how the fluids act.
Thank you so much!
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2 Replies Last Post Apr 12, 2011, 12:02 p.m. EDT
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Posted:
1 decade ago
Hi
the inlet is where you have a flow going through, I do not believe this should be the case for the wall in the fluid section
for the "inlet 1" your velocity formula is OK for a single edge segment, you have 3 so you will have a triple parabolic velocity profile so something like
velocity = u_max*4*y*(4[mm]-y)
should be better (pls check carefully the shape and I always forget if its *6, *4, or *2 for the peak to average value)
Fixed and prescribed displacement =0 are the same conditions (underneath)
Your model looks, for me too much like a 3.5 translation that is not "optimal". I would rather run the model library MEMS Fluid Structure Interaction example, then copy your geometry only into a new v4 model (and I believe the geometry could be slightly wrong, I do not understand what these cut lines are for, and if they are at the right place: looks like 34, 35, 12 should be closer to edges 46,47 ?, but OK, not my model ;) And reconstruct it from scratch in V4, following the FSI example. I believe it would be more efficient for you
--
Good luck
Ivar
the inlet is where you have a flow going through, I do not believe this should be the case for the wall in the fluid section
for the "inlet 1" your velocity formula is OK for a single edge segment, you have 3 so you will have a triple parabolic velocity profile so something like
velocity = u_max*4*y*(4[mm]-y)
should be better (pls check carefully the shape and I always forget if its *6, *4, or *2 for the peak to average value)
Fixed and prescribed displacement =0 are the same conditions (underneath)
Your model looks, for me too much like a 3.5 translation that is not "optimal". I would rather run the model library MEMS Fluid Structure Interaction example, then copy your geometry only into a new v4 model (and I believe the geometry could be slightly wrong, I do not understand what these cut lines are for, and if they are at the right place: looks like 34, 35, 12 should be closer to edges 46,47 ?, but OK, not my model ;) And reconstruct it from scratch in V4, following the FSI example. I believe it would be more efficient for you
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi, Dr. Ivar
Thank you for your patience and time to help me all the time, really appreciated!
First, maybe due to the funding, my professor didn't buy the MEMS model. And she think we can do it by combining these models, so you know, once professor says, then " I have to follow and try to figure it out ".
Second, for the wall that between the fluid and the solid membrane, what kind of boundary should I use id I don't use the "Inlet", should I use Wall---Moving Wall----set Uw as u2 and v2?
In 3.5a, I know there are many differences, but at least if I can run a model in 3.5a, I also should transfer it in version 4. right?
Third, for the inlet 1,3,5, I set them to be the same conditions, so I can not understand your comments
" a triple parabolic velocity profile so something like velocity = u_max*4*y*(4[mm]-y) ", I think I can choose them like a group/ section, and set the same boundary.
Forth, the 34, 35,12 and 46, 47 are the repeated part, sorry for the confusion, it describes the repeated valves in our vein systems, in my geometry, I only draw a single valve, the domain 8 and 13 are the valve leaflets that can behave flexible, when blood comes from left to right, it opens, then close.
so the unneeded line may should be the line 18 17 21 23 11 14 28 29 , still I am not so confident in Comsol, so I just see my senior lab mate draw like this in 3.5a, and run the model really good, I drawn the geometry as her.
Also because her model in 3.5a has some experimental data to match, and I really want to model it in version4, and begin my new experiments.
Thank you, Mr. Ivar, I feel that I brought so much trouble to you!
I attached my new file, which I do some changes! Still run with error! Feeling so sad!
Thank you from the bottom of my heart!
Thank you for your patience and time to help me all the time, really appreciated!
First, maybe due to the funding, my professor didn't buy the MEMS model. And she think we can do it by combining these models, so you know, once professor says, then " I have to follow and try to figure it out ".
Second, for the wall that between the fluid and the solid membrane, what kind of boundary should I use id I don't use the "Inlet", should I use Wall---Moving Wall----set Uw as u2 and v2?
In 3.5a, I know there are many differences, but at least if I can run a model in 3.5a, I also should transfer it in version 4. right?
Third, for the inlet 1,3,5, I set them to be the same conditions, so I can not understand your comments
" a triple parabolic velocity profile so something like velocity = u_max*4*y*(4[mm]-y) ", I think I can choose them like a group/ section, and set the same boundary.
Forth, the 34, 35,12 and 46, 47 are the repeated part, sorry for the confusion, it describes the repeated valves in our vein systems, in my geometry, I only draw a single valve, the domain 8 and 13 are the valve leaflets that can behave flexible, when blood comes from left to right, it opens, then close.
so the unneeded line may should be the line 18 17 21 23 11 14 28 29 , still I am not so confident in Comsol, so I just see my senior lab mate draw like this in 3.5a, and run the model really good, I drawn the geometry as her.
Also because her model in 3.5a has some experimental data to match, and I really want to model it in version4, and begin my new experiments.
Thank you, Mr. Ivar, I feel that I brought so much trouble to you!
I attached my new file, which I do some changes! Still run with error! Feeling so sad!
Thank you from the bottom of my heart!
Attachments: