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October 9, 2014, 07:53 |
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#61 |
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Dear Bruno,
lots of thanks for your help. I really appreciated. I'm still looking for the result. I followed what you posted in the previous post. I would like to make sure about answering some questions please 1. How to plot xy displacement to make sure if some movement, might there is movement but I couldn't figure out? 2. Is anchor the initial distance? 3. What about refAttachementPt, is it the same as anchor? From the definitions they should be different, is that correct? 4. Is the spring in the inlet? 5. What other for more clarification? Looking forward to get your help. Thanks in advanced and regards. Maimouna |
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October 11, 2014, 15:03 |
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#62 | ||
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Hi Maimouna,
Quote:
Quote:
It was hand drawn, so it's not accurate. This example has the pendulum at a stationary position, i.e. it will not move unless it is disturbed. As for the locations of the anchor and the reference point:
I'm not sure I understood your question, but I believe that the answer is: No, it's not in the inlet. If I remember correctly, I ended up placing the anchor in the same exact location where the centre of the cylinder is at the starting position. As I mentioned above, it was because it was easier/convenient. Sorry, I didn't understand this question. Best regards, Bruno |
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October 12, 2014, 07:23 |
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#63 |
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Dear Bruno,
many thanks for your reply. In question #5 What other for more clarification? I meant that if you have some other tutorials to follow to help me to get the answer of that case. I'm really strange that there is no body did such this case in OpenFOAM. I started searching for that since last April and I couldn't get the answer till today. I'm really worry about that because I have limited time to finish that. Please help. Many thanks in advanced. Maimouna |
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October 12, 2014, 12:29 |
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#64 | |
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Hi Maimouna,
Quote:
The information I told you about in the last few posts isn't something new, it's a collection of information that has been in OpenFOAM for quite sometime now. I merely interpreted some of it and simplified the case you had. You were on the right path, but it seems to me that you were trying to deal with too much complexity in a single step. I don't know what you know so far and what you've found in all of these months. But in case you don't know, there is an unofficial wiki for OpenFOAM at http://openfoamwiki.net - there you can find this page: http://openfoamwiki.net/index.php/Handy_links - and in that page there are links to "Håkan Nilsson's PhD course", in which there are several small reports by PhD students. I believe that possibly somewhere in those reports there was something that could have helped you at least figure out how you could try to deduce where to find the solution to your problem. And as many of those reports show, the writer of the report had to do a lot of trial and error, building slowly from a simpler problem to the more complex problem. From personal experience, most of the things I know about OpenFOAM were not from courses, it was from trial-and-error, and messing around with OpenFOAM's tutorials and code. And much of it has been because I've been helping out people on the forum, with little tasks most weekends and vacations. And this has mostly been done in my free time and unfortunately my free time is becoming more and more reduced... Sorry, but all of this to say: the answers you are looking may very well already be answered in OpenFOAM's own tutorials and source code. Other answers will reveal themselves if you try to evolve your case slowly, one step at a time. And continue to look around OpenFOAM's tutorials and so on. Good luck! Best regards, Bruno |
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October 25, 2014, 16:25 |
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#65 |
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Dear Bruno,
the case attached is the last thing that I got. Could you please check it for me if it is make sense. Because I need to move to the next step which it depends on it. If you could get some of your precious time to go through it, that would be really grateful. Many thanks in advanced and regards. Maimouna |
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December 8, 2014, 05:17 |
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#66 |
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Hi Maimouna,
I'm looking right now at the file "pointDisplacement" and there is something very critical that is missing in all of this: What is the real physical representation of your cylinder? In other words, how exactly are the springs meant to be attached to the cylinder and to the walls of the surrounding environment? Do you have a schematic drawing of the connections between the cylinder, the springs and the surrounding walls? ------------------------- edit: I had hoped you were online for answering the question at the time of the initial version of this post, but I guess not. So here's what I figured that needs to be explained, namely through a visual medium. Keep in mind that you're trying to simulate something that's real, which means that you'll need to deploy constraints based on a realistic experimental structure. This is what I've not seen in your questions and which I'll have to outline myself, in order to define both the intermediate concept and final implementation. Attached are 2 images, which for the sake of completeness, also include the representation of a generic pipe (er, a large black rectangle) and a block cylinder near the centre. The description for each image is as follows:
Best regards, Bruno Last edited by wyldckat; December 8, 2014 at 06:00. Reason: see "edit:" |
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December 8, 2014, 06:31 |
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#67 |
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Dear Bruno,
lots of thanks for your post. Now, I'm going carefully to understand what you post. Waiting for your next post about definition for pointDisplacement file. Many thanks and regards. Maimouna |
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December 8, 2014, 09:20 |
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#68 |
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Dear Bruno,
come back to your questions. I didn't have my own schematic drawing of the connections between the cylinder, the spring and the walls. I just tried to follow some schematics found on papers such as the one that mentioned in http://waset.org/publications/11024/vortex-induced-vibration-characteristics-of-an-elastic-circular-cylinder but using my own bounding box. I'm sure that does not make sense that was my fault, but I couldn't find that much to explain me cylinder, spring and surrounding walls. Sorry for that stupid situation. I hope I could understand more from you or from other foamers to get the answer. Best regards Maimouna |
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December 8, 2014, 11:56 |
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#69 | |
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Hi Maimouna,
I ended up having a few setbacks and didn't manage to write everything in a single go. Quote:
So I was looking at this paper and when I saw Figure 1, I bursted into laughs... just in case the paper goes away for some reason, Figure 1 is this one: If you look at the first figure on my previous post, this will look reaaaaaaaaaaaaally familiar at least to me, because of the drawing I made and which might not be fully understandable, but is nearly identical... The difference is that I was thinking of having all of the springs with the same specifications, namely both stiffness and damping. In the paper's schematic, 2 springs only have stiffness and then the 2 other are dampers. Now, the first big question: Why use the cross-like structure? The answer is simple (using my earlier drawing from the previous post): because if only 2 springs are used on each direction, for example, if only S1 and S2 existed, this would mean that the cylinder could potentially escape to the upper left corner, by passing through the middle point between A1 and A2. OK, the file settings for each scenario, at least conceptually, it should be something like this:
Best regards, Bruno Last edited by wyldckat; December 31, 2014 at 14:51. Reason: added "fixedOrientationCoeffs" to "fixedOrientation" |
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December 9, 2014, 06:20 |
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#70 |
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Dear Bruno,
lots of thanks for your post. I tried them all. They all work fine except scenario2 gives me error in sixDoFRigidBodyMotionConstraint fixedOrientation; but when committing it, works fine. Now, I'm working to see changes and comparison with other results. I have one more question please, is it possible to change to one or two degrees of freedom? What could I do to work in one or two degrees of freedom in the same file? Many thanks for your help and regards. Maimouna |
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December 10, 2014, 15:12 |
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#71 | ||
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Quick answers:
Quote:
Quote:
I ask this because Scenarios 1 and 3 have technically 2 degrees of freedom; Scenario 2 is meant to have only 1 degree of freedom. |
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December 11, 2014, 06:24 |
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#72 | |
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Quote:
If scenario 1 and 3 have 2 DOF and scenario 2 has 1 DOF, why cylinder in pointDisplacement file is type of sixDoFRigidBodyDisplacement? Sorry, that might be a stupid question but I need to understand how it works exactly. Many thanks for your help. Best regards Maimouna |
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December 13, 2014, 16:14 |
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#73 | |
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Hi Maimouna,
Quote:
OK, imagine this:
The restraints will restrain DoFs, mostly by applying springs and dampers. As for "sixDoFRigidBodyDisplacement": this is implemented in a CFD code, namely OpenFOAM, therefore it makes sense to implement the code for the general solution, instead of coding each individual possibility. It would be mind boggling to have over 100 combinations of DoFs implemented... Best regards, Bruno |
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December 14, 2014, 05:52 |
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#74 |
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Dear Bruno,
lots of thanks for your explanation. Waiting for you to test all three scenarios when you get time for more clarification. I started testing them for different cases with different bounding boundaries and boundary conditions. Lots of thanks in advanced and kind regards. Maimouna |
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December 31, 2014, 15:55 |
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#75 | |
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Bruno Santos
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Greetings Maimouna,
Quote:
The only problem that scenario 2 had was the there was a small detail missing... I've rectified post #69: Code:
DontRotate { //Warning: Only valid where the predicted deviation from alignment is < 90 degrees. sixDoFRigidBodyMotionConstraint fixedOrientation; tolerance 1e-06; relaxationFactor 0.7; fixedOrientationCoeffs { //This is necessary, even if kept empty } }
Bruno -------------- edit: Note to careless readers: these cases that are attached will likely only work on OpenFOAM 2.2.2 and 2.2.x. For more details, read the posts above as well. Last edited by wyldckat; February 10, 2015 at 14:35. Reason: see "edit:" |
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January 28, 2015, 05:39 |
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#76 |
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Dear Bruno,
many thanks for your help and sorry for late reply. I was away and have limited connection to the internet. After free oscillation for the rigid cylinder, now, I'm trying to do the same for the elastic (flexible) cylinder. I have some questions for that please 1. Have I solved the elastic equation for the solid part? If yes, where exactly have solved that equations using OpenFOAM? 2. It is important that to mesh inside the cylinder. What can add to mesh inside the cylinder in my previous .geo file? Any idea please with lots of thanks in advanced. Maimouna |
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January 28, 2015, 15:23 |
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#77 | |||
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Hi Maimouna,
Quote:
Quote:
Quote:
Best regards, Bruno |
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February 3, 2015, 09:16 |
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#78 |
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Dear Bruno,
I add part of meshing cylinder in geo file as shown in the attached pictures. Checking mesh was fine. But, adding that new geo file shown below Code:
D = 1; R = 0.5*D; CX = 4*D; CY = 0.0; S = 1.0/Sqrt(2); DR1 = R*S; DR2 = (R + 2.0*D)*S; Point(1) = {0, -4*D, 0}; Point(2) = {0, CY - DR2, 0}; Point(3) = (0, CY + DR2, 0); Point(4) = {0, 4*D, 0}; Point(5) = {CX - DR2, -4*D, 0}; Point(6) = {CX - DR2, CY - DR2, 0}; Point(7) = {CX - DR2, CY + DR2, 0}; Point(8) = {CX - DR2, 4*D, 0}; Point(9) = {CX - DR1, CY - DR1, 0}; Point(10) = {CX - DR1, CY + DR1, 0}; Point(11) = {CX, CY, 0}; Point(12) = {CX + DR1, CY - DR1, 0}; Point(13) = {CX + DR1, CY + DR1, 0}; Point(14) = {CX + DR2, -4*D, 0}; Point(15) = {CX + DR2, CY - DR2, 0}; Point(16) = {CX + DR2, CY + DR2, 0}; Point(17) = {CX + DR2, 4*D, 0}; Point(18) = {16*D, -4*D, 0}; Point(19) = {16*D, CY - DR2, 0}; Point(20) = {16*D, CY + DR2, 0}; Point(21) = {16*D, 4*D, 0}; Point(22) = {0, CY, 0}; Point(23) = {CX - 2*D, CY, 0}; Point(24) = {CX + 2*D, CY, 0}; Point(25) = {16*D, CY, 0}; Point(26) = {CX, -4*D, 0}; Point(27) = {CX, CY - 2*D, 0}; Point(28) = {CX, CY + 2*D, 0}; Point(29) = {CX, 4*D, 0}; Point(30) = {CX, CY - R, 0}; Point(31) = {CX - R, CY, 0}; Point(32) = {CX, CY + R, 0}; Point(33) = {CX + R, CY, 0}; Line(1) = {4, 8}; Line(2) = {8, 29}; Line(3) = {29, 17}; Line(4) = {17, 21}; Line(5) = {21, 20}; Line(6) = {20, 25}; Line(7) = {25, 19}; Line(8) = {19, 18}; Line(9) = {18, 14}; Line(10) = {14, 26}; Line(11) = {26, 5}; Line(12) = {5, 1}; Line(13) = {1, 2}; Line(14) = {2, 22}; Line(15) = {22, 3}; Line(16) = {3, 4}; Line(17) = {3, 7}; Line(18) = {7, 8}; Line(19) = {2, 6}; Line(20) = {6, 5}; Line(21) = {15, 14}; Line(22) = {15, 19}; Line(23) = {16, 17}; Line(24) = {16, 20}; Line(25) = {25, 24}; Line(26) = {23, 22}; Line(27) = {28, 29}; Line(28) = {27, 26}; Line(29) = {27, 15}; Line(30) = {15, 24}; Line(31) = {24, 16}; Line(32) = {16, 28}; Line(33) = {28, 7}; Line(34) = {7, 23}; Line(35) = {23, 6}; Line(36) = {6, 27}; Line(37) = {30, 27}; Line(38) = {31, 23}; Line(39) = {33, 24}; Line(40) = {32, 28}; Line(41) = {10, 7}; Line(42) = {9, 6}; Line(43) = {13, 16}; Line(44) = {12, 15}; Circle(45) = {31, 11, 10}; Circle(46) = {10, 11, 32}; Circle(47) = {32, 11, 13}; Circle(48) = {13, 11, 33}; Circle(49) = {33, 11, 12}; Circle(50) = {12, 11, 30}; Circle(51) = {30, 11, 9}; Circle(52) = {9, 11, 31}; Line Loop(53) = {17, 18, -1, -16}; Ruled Surface(54) = {53}; Line Loop(55) = {33, 18, 2, -27}; Ruled Surface(56) = {55}; Line Loop(57) = {32, 27, 3, -23}; Ruled Surface(58) = {57}; Line Loop(59) = {24, -5, -4, -23}; Ruled Surface(60) = {59}; Line Loop(61) = {25, 31, 24, 6}; Ruled Surface(62) = {61}; Line Loop(63) = {30, -25, 7, -22}; Ruled Surface(64) = {63}; Line Loop(65) = {8, 9, -21, 22}; Ruled Surface(66) = {65}; Line Loop(67) = {21, 10, -28, 29}; Ruled Surface(68) = {67}; Line Loop(69) = {11, -20, 36, 28}; Ruled Surface(70) = {69}; Line Loop(71) = {12, 13, 19, 20}; Ruled Surface(72) = {71}; Line Loop(73) = {19, -35, 26, -14}; Ruled Surface(74) = {73}; Line Loop(75) = {34, 26, 15, 17}; Ruled Surface(76) = {75}; Line Loop(77) = {42, -35, -38, -52}; Ruled Surface(78) = {77}; Line Loop(79) = {36, -37, 51, 42}; Ruled Surface(80) = {79}; Line Loop(81) = {29, -44, 50, 37}; Ruled Surface(82) = {81}; Line Loop(83) = {44, 30, -39, 49}; Ruled Surface(84) = {83}; Line Loop(85) = {39, 31, -43, 48}; Ruled Surface(86) = {85}; Line Loop(87) = {43, 32, -40, 47}; Ruled Surface(88) = {87}; Line Loop(89) = {46, 40, 33, -41}; Ruled Surface(90) = {89}; Line Loop(91) = {38, -34, -41, -45}; Ruled Surface(92) = {91}; RHO1 = 20; // Vertical near-wall parts RHO2 = 15; RHO3 = 15; RHO4 = 100; // Outlet channel RHO5 = 20; RHO6 = 20; // Inlet channel RHO7 = 30; Transfinite Line {13, 20, 28, 21, 8} = RHO1; Transfinite Line {16, 18, 27, 23, 5} = RHO1; Transfinite Line {15, 34, 45} = RHO2; // Dense mesh in the middle Transfinite Line {48, 6} = RHO7 Using Progression 0.97; Transfinite Line {31} = RHO7 Using Progression 1.03; Transfinite Line {14, 35, 52} = RHO2; // Dense mesh in the middle Transfinite Line {49, 7} = RHO7 Using Progression 1.03; Transfinite Line {30} = RHO7 Using Progression 0.97; Transfinite Line {11, 36, 51, 46, 33, 2} = RHO3; Transfinite Line {10, 29, 50, 47, 32, 3} = RHO3; Transfinite Line {9, 22, 25, 24, 4} = RHO4; Transfinite Line {42, 37, 44, 39, 43, 40, 41, 38} = RHO5 Using Progression 1.02; Transfinite Line {1, 17, 26, 19, 12} = RHO6; Transfinite Surface "*"; Recombine Surface "*"; Extrude {0, 0, D} { Surface{54, 76, 74, 72, 70, 80, 78, 92, 90, 56, 58, 88, 86, 84, 82, 68, 66, 64, 62, 60}; Layers{1}; Recombine; } Line Loop(533) = {52, 45, 46, 47, 48, 49, 50, 51}; Plane Surface(534) = {533}; cylindervolume[]={Extrude {0, 0, D} { Surface{534}; Layers{1}; Recombine; } }; //cylindervolume[] is a list //with this naming policy i do not need to know the volume ID to set a group on it Physical Surface("inlet") = {113, 131, 157, 171}; Physical Surface("outlet") = {453, 483, 509, 523}; Physical Surface("walls") = {167, 189, 435, 457, 527, 329, 307, 109}; Physical Surface("cylinder") = {417, 399, 377, 219, 245, 267, 277, 355}; Physical Surface("top") = {114, 136, 158, 180, 202, 444, 466, 488, 510, 532, 334, 312, 246, 224, 422, 400, 378, 356, 290, 268}; Physical Surface("bottom") = {54, 76, 74, 72, 70, 68, 66, 64, 62, 60, 58, 56, 92, 78, 80, 82, 84, 86, 88, 90}; Physical Volume("channel") = {5, 4, 3, 7, 6, 15, 16, 14, 17, 18, 19, 20, 11, 12, 13, 9, 8, 10, 1, 2}; Physical Volume("cylinderv") = cylindervolume[]; //Mesh 3; Save "elastic_cylinder-2D.msh"; For more clarification about elastic (flexible) cylinder, the shape of the elastic cylinder will change when any force affects on it. I'm looking to see that in paraview. Thanks in advanced and regards. Maimouna Last edited by wyldckat; February 3, 2015 at 14:55. Reason: Changed [QUOTE][/QUOTE] to [CODE][/CODE] |
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February 7, 2015, 07:29 |
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#79 | ||||
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Bruno Santos
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Greetings Maimouna,
Quote:
Quote:
In addition, the geo file you provided did not generate a mesh for me. In case you're not aware, you can compress the geo file to a ZIP file and attach the zip file to the post. Quote:
Quote:
Don't understand why I asked you for a 100-500 word description on what you're specifically asking about? I'll tell you:
Please, this is not a doctor's office where you come in to ask for a solution for a headache in your head and expect a pill for the pain to be the solution to the problem. Best regards, Bruno |
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February 8, 2015, 07:40 |
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#80 | |
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Dear Bruno,
Quote:
I'm so sorry about less descriptive about elastic circular cylinder. I'm still reading to get the full description. The topic that I would like to find out the results is the same topic that discussed before for rigid cylinder, but this time (Vortex-induced vibration of an elastic cylinder). In the elastic cylinder topic, I have to use the dynamic elastic equation which I think discussed in FSI library of OpenFOAM. For the elastic cylinder we should find displacements inside cylinder at all nodes. When I search about solving FSI problem using OpenFOAM, I could end up with using such FSI solvers in foam-extend-3.1. Because there are lots of structural solvers in that foam version. Take for example HronTurekFsi case in icoFsiElasticNonLinULSolidFoam solver in silidMechanics tutorial. I'm not sure if I right or not but that what I'm studying at the moment to understand icoFsiElasticNonLinULSolidFoam environment and then making some changes regarding my case. If you could help me and give me some advice to guide me to the right way, I would be really appreciated. Kind regards |
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