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December 14, 2015, 01:05 |
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#121 |
New Member
Jason
Join Date: Dec 2015
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Rep Power: 10 |
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December 14, 2015, 09:04 |
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#122 |
Senior Member
ok
Join Date: Oct 2013
Posts: 346
Rep Power: 13 |
Code:
1. Follow your method below, I can only get the x of the mass center. Do you know how to get all x y z? 2. For the attached case, I can find the cylinder is moving, but velocity and displacement are very small (the order is e-6 to e-9). I tried to change the mass, stiffness and damping but none of them works. Can you give me suggestions to make the cylinder move more obviously? 1. As posted, I'm still not sure if there is a way to get all components. Might there is some expertises could help me, you and others. 2. Try one by the time, I mean try to change mass first, if doesn't work change stiffness and then damping or what ever you would like to begin with. Honestly, I don't have time to test that with you, so try them and let me know if that work or not. Just in case getting time in the next few days, send me your case study problem (domain, BCs, Re, all possible information) to have a look. All the best Maimouna |
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December 14, 2015, 09:31 |
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#123 |
Senior Member
ok
Join Date: Oct 2013
Posts: 346
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Code:
1. Follow your method below, I can only get the x of the mass center. Do you know how to get all x y z? Code:
set title "Centre of Mass" set ylabel 'Centre of Mass' set xlabel 'Iteration' set yrange [-3:4.1] plot"< cat log | grep 'of mass' | cut -d' ' -f5 | tr -d ' '" every::::1000 title 'Centre of Mass (y)' with lines,\ "< cat log | grep 'of mass' | cut -d'(' -f2 | tr -d ' '" every::::1000 title 'Centre of Mass (x)' with lines,\ "< cat log | grep 'of mass' | cut -d' ' -f6 | tr -d ')'" every::::1000 title 'Centre of Mass (z)' with lines pause 1 set terminal jpeg set output 'Centre of Mass.jpeg' reread replot Kind regards Maimouna |
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December 15, 2015, 02:21 |
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#124 | |
New Member
Jason
Join Date: Dec 2015
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Thanks, Maimouna! That's a great help!
Regards Jason Quote:
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December 20, 2015, 23:43 |
oscillating cylinder dynamic mesh
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#125 |
Senior Member
Join Date: Jan 2013
Posts: 135
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Have someone tried 2nd order temporal accuracy in the vortex induced vibration cases? The wingMotion tutorial used Euler, which is a first order ddtScheme. In my VIV around a circular cylinder case, when I change it to a 2nd order accurate backward, the computation diverged!
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December 21, 2015, 07:54 |
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#126 |
Senior Member
Jan
Join Date: Jul 2009
Location: Hamburg
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Short answer: yes
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December 21, 2015, 09:14 |
no damping effects in free decay test
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#127 |
New Member
Agnese Paci
Join Date: May 2015
Location: Bologna, Italy
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Hi everybody!
I'm simulating free decay tests of a vertical floating cylinder in OF 2.3.0, with interDyMFoam. The cylinder is moored to the bottom with four linear springs. it works, but it seems to be not realistic, because the motion is almost not dampened. Did anybody work on this topic? can you suggest me the reason or the way to solve the problem? Thank you very very much in advance. Agnese |
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December 21, 2015, 09:44 |
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#128 |
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January 19, 2016, 23:44 |
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#129 | |
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Jason
Join Date: Dec 2015
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Quote:
Can you upload your case file so that we can have a discuss? |
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May 17, 2016, 20:21 |
where is the aerodynamics coefficients implemented?
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#130 |
New Member
Sergio
Join Date: May 2016
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Hi everyone!! I am new in this forum, because I am trying to learn OpenFoam, and I find this information very useful to my case, so thank you to all.
Well, I am reading and practice this example using gmsh to mesh and trying to get something good, but i have a question, Where is implemented all the aerodynamics coefficients? Because I have seen how this example give me some drag coefficients and lift coefficients , but i don't know how I can use to another case. So where is the lift, in the fvSolution and fvSchemes? Thank you in advance for any help you can give! Xjokjok |
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May 18, 2016, 01:32 |
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#131 | |
Senior Member
Join Date: Jun 2012
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Quote:
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May 18, 2016, 12:48 |
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#132 |
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Sergio
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May 19, 2016, 03:37 |
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#133 | |
New Member
Jason
Join Date: Dec 2015
Posts: 12
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Hi
Lift and drag coefficients should be output from the calculation of OpenFOAM, not the input. For input, such as stiffness, damping, they are defined in dynamicMeshDict file in constant folder. Quote:
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July 8, 2016, 03:51 |
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#134 | |
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Divyaprakash
Join Date: Jun 2014
Posts: 70
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Quote:
I too am in need of a validation case to validate my model in openfoam. Did you have any luck with it? Can you help me out too? |
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September 6, 2016, 11:13 |
Doubts about report 6-DoF
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#135 |
New Member
Catalina Valencia
Join Date: Sep 2015
Posts: 9
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Hi everyone,
I've been working with free cylinder in an oscillating flow. I'm using 6-DoF rigid body motion with transverse direction of flow (y) allow to move. No matter what I do, the log file not contains information about 6-DoF such as centre of mass that I need to capture the movement. I put on the report and the reportToFile too but nothing. I using openFOAM 2.4, ubuntu 14.04 LTS. Then I installed openFOAM 3.0 to try to overcome the error. But nothing change I will be very grateful with your help. Best regards dynamicMeshDict file: Code:
dynamicFvMesh dynamicMotionSolverFvMesh; motionSolverLibs ( "libsixDoFRigidBodyMotionDev.so" "libfvMotionSolvers.so" ); solver sixDoFRigidBodyMotion; sixDoFRigidBodyMotionCoeffs { patches (cylinder); //innerDistance 0.008; //outerDistance 0.01; mass 10; centreOfMass (0 0 0); momentOfInertia (6.4e-04 6.4e-04 1.28e-03); orientation ( 1 0 0 0 1 0 0 0 1 ); velocity (0 0 0); acceleration (0 0 0); angularMomentum (0 0 0); torque (0 0 0); rhoName rhoInf; rhoInf 1; g (0 0 -9.81); report on; reportToFile on; constraints { maxIterations 500; Line { sixDoFRigidBodyMotionConstraint line; direction (0 1 0); } /*DontMoveOverZ { sixDoFRigidBodyMotionConstraint axis; axis (0 0 1); }*/ } restraints { S2 { sixDoFRigidBodyMotionRestraint linearSpring; linearSpringCoeffs { anchor (0 0.01 0); refAttachmentPt (0 0 0); stiffness 2; damping 0; restLength 0.01; } } } } Code:
dimensions [0 1 0 0 0 0 0]; internalField uniform (0 0 0); boundaryField { inlet { type fixedValue; value uniform (0 0 0); } outlet { type fixedValue; value uniform (0 0 0); } top { type empty; } bottom { type empty; } frontAndBack { type empty; } cylinder { type calculated; } } 1000_T100.png Last edited by CataV; September 6, 2016 at 20:42. |
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September 6, 2016, 12:09 |
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#136 | |
New Member
behzad
Join Date: Dec 2010
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Quote:
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September 6, 2016, 17:21 |
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#137 |
New Member
Catalina Valencia
Join Date: Sep 2015
Posts: 9
Rep Power: 10 |
Hello Behzad
Many thanks to replay. You can find 2 attachments bellow, with openFOAM 2.4: https://drive.google.com/folderview?...ms&usp=sharing 1. oscillating_1000_1: the dynamicMeshDict file has a sixDoFRigidBodyMotion as the solver and the sixDoFRigidBodyMotionCoeffs are presented here. 2. oscillating_1000_2: the pointdisplacement file has the sixDoFRigidBodyMotionCoeffs and dynamicMeshDict has a displacementLaplacian as the solver. I tried to use both ways that I found in some forums and I changed thinks like mass, stiffness and restLength but the movement of the cylinder is not displayed and there isn't 6-DoF data information in log file. I'll be waiting for any idea to solve my problem Thanks... Last edited by CataV; September 6, 2016 at 20:43. |
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September 6, 2016, 23:59 |
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#138 | |
New Member
behzad
Join Date: Dec 2010
Posts: 15
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Quote:
https://drive.google.com/file/d/0B5M...ew?usp=sharing |
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September 7, 2016, 05:24 |
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#139 | |
New Member
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Quote:
Similar to the discussions in this thread, I am simulating the cube shaped object vibrating along only one axis (oscillating)in water. I used linearSpring. I can successfully make it vibrate (free vibrations without damping) at its natural frequency (calculated from stiffness and mass), and validated with the analytical calculations. Now I want to add an external force so that the object will vibrate at various frequencies other than its natural frequency. One attempt: I tried to modify restraintforce equation in the linearSpring.C file, by adding the external force term F0*sin(wt), but it didn't work may be because I couldn't add "time, t" in there. What do you suggest to solve this problem? Many thanks in advance. Best regards, Sachin |
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September 8, 2016, 23:23 |
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#140 | |
New Member
Catalina Valencia
Join Date: Sep 2015
Posts: 9
Rep Power: 10 |
Quote:
Thank you very much for your help. I saw your changes, comments and log file. Everything seems to be good. So I proved the model that you send me and the log file doesn't show any information about 6-DoF or mass center. Maybe there is a problem with the OF instalation or some libraries are missing, I don't know For installing OF I used this link https://openfoamwiki.net/index.php/I...M-2.4.0/Ubuntu for Ubuntu 14.04 and install from source For running I generat the mesh with "blockMesh" and then I enter the command line "pimpleFoam" I'll be waiting for a comment Thanks again |
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