Learning Forum

[hula]

Hello everybody,

I would like to study the fluid-structure interaction. Thanks to Ansys I want to get the free modes of vibration of a cantilever beam immersed in a rectangular water tank. I have already get the modes of vibration of a dry beam. Indeed it is quite easy because there is lot of tutorials available on YouTube but I would like to get the modes of vibration of an immersed cantilever beam. My goal is to compare frequencies between the two situations with and without water for the first mode, second mode and third mode... I have used Transcient Structural, Modal, Fluid Flow (Fluent) and System Coupling to do this. I have found two videos to help me on YouTube "ANSYS System Coupling: Two Way Fluid Structure Interaction" Part 1 and Part 2. But I still don't understand how to do this and I am a beginner on Ansys. I just begin on it. Is someone available to show me how to do this (step by step) ? Tutorials on YouTube are not clear...and currently there is no well explanations to my questions on the student community.

Thank you for your help. I am looking forward to hearing from you soon !

Best regards.

[Karthik Remella]

Hello,

I'm glad you found those two videos on how to set-up a Two Way Fluid-Structure interaction. I'd recommend you follow the steps outlined in these two videos and set-up a simple problem to learn the set-up process first. Once you are comfortable with the process and the workflow, I'd then go and use these tools to model the problem you are talking about. Once you develop familiarity with 'how-to-setup', you should be able to set up your model fairly quickly.

If you need any additional 'specific' help during your modeling process, please feel free to create another question and we will be happy to help you.

I hope this helps.

Best,

Karthik 

[hula]

Thank you very much Kremella !!!

I watched carefully the two videos on YouTube “Analyzing FSI with CFX and Mechanical” but I have still difficulties to do it (link :

)

Firstly,I connected the 3 different analysis systems : Transcient Structural, Fluid Flow (CFX) and System Coupling. Secondly,I went into geometry and I create my beam and I use enclosure to create my water tank(= my fluid domain). Thirdly, in Transcient Structural I went in model I put a fixed support on a face because I study a cantilever beam. Then, I put a fluid solid interface and pressure on faces. The value of the pressure is equal to 0 MPa and the software told me that the “magnitude” is invalid when I click on generate and I don’t understand this. Always, in Transcient Structural I create a mesh and I click on Meshing and it seems to be Ok for the beam. In transcient Structural, I considered only the beam and not the water tank I have clicked on “suppress body” to have this. Moreover, in analysis settings in Transcient Structural I used the same parameters like in the first video for step end time (=10s) and number of Substeps =1.

According to the 2 videos, then I went on setup in Fluid Flow (CFX) and I choose System Coupling  for the mesh motion. I used the same parameters like in the video part 2 (total time=10s and timesteps=0,1s). But the software show me an error “Value of 'Timesteps' in object '/FLOW:Flow Analysis 1/ANALYSIS TYPE/TIME STEPS', '0 , 1 ', violates its lower bound, '1.0E-30 '.”

In the workbench, I can see that the meshing seems to be OK for fluid flow (CFX) but I have not create a mesh by myself for the fluid domain and it is quite strange for me. I don’t understand that.

Moreover, I have a problem when I go in System Coupling because I can not see participants and I can not progress in the following steps indicated in the part 2 of the video.

I hope you will help me. Thank you for your help !

I am looking forward to hearing from you.

Best regards.

[hula]

[hula]

[hula]

[Gumang]

hey,ni am also working on the same problem(Modal analysis of immersed structures). Did you figure it out? if yes could you please help me and share how you set up the FSI and the coupling. I also tried these 2 videos. but did not really understand how to use this for my/ours case. nbest Regards nUmang

[jesse.liu]

 

Karthik R, I have the similar question. I would like to calcualte the nature frequencies of a beam immersed in water at the steady state rather than tje transient state. Can you please provide the instructions by steps? or would you please send me one example of the model?

Thanks in advance.

Best regards,

J LIU

 

 

[Rukmini Sai Rupa Sri Mada]

Hello everyone,

I would like to perform a fluid-solid interface on a cantilever beam with piezo excitation. I have modeled a t-shaped structure that is actuated by bimorph piezo patches at the fixed end. This end acts as a fixed end and the structure will be immersed in water completely and would like to see the mode shapes of this structure. I have already performed modal analysis on this structure and now want to simulate it in a water ambiance. I also want to know if using modal acoustics serves the purpose as I am not aware of ANSYS fluent at all. Also, does this have any added mass effect if the water has some flow induced in it? If so how can this effect be simulated in ANSYS? Please let me know.

Thanks in advance

Rupa

[Rukmini Sai Rupa Sri Mada]

 

https://drive.google.com/file/d/1sMnZvfn-zp5ZZ3O3jfn4s7Y_3rRYmaPb/view?usp=sharing

Hello everyone,

I’m currently working on the Fluid-Structure Interaction (FSI) simulation of a T-shaped structure in Modal acoustics within a spherical enclosure. However, I’ve run into some roadblocks with numerous warnings and errors, and I’m struggling to obtain meaningful results. Specifically, I’m curious about strategies for resolving the warnings and errors that are hindering my progress. Additionally, I’m uncertain about the best approach to attain accurate damping frequency values in this context.

In this simulation, I have used modal acoustics to obtain the damping modal frequencies of the structure in water ambiance. For this, I imported a T-shaped structure and then created a spherical enclosure in the design modeler. The T-shaped structure assigned with stainless steel material acts as a cantilever beam and is fixed at the free end of the stem of T.  The spherical enclosure is assigned with water liquid as its material. This structure acts as a structural/physics region whereas the spherical enclosure acts as an acoustics region and its surface is assigned as an absorption element. A Fluid-Structure interface is generated over the faces of the T-shaped structure which are in contact with water liquid (Spherical enclosure). When the simulation is performed with the above conditions, I expect to get the modal response of the structure in a water environment/enclosure.

If anyone has experience with FSI in modal acoustics or can point me in the right direction, your input would be immensely valuable.

These are the warnings from the simulation run.

 *WARNING*: The geometric gap/penetration may be too large.  Increase    
 pinball radius if it is a true geometric gap/penetration.  Decrease     
 pinball if it is a false one.            

                              
 *WARNING*: The initial penetration/gap is detected which may cause      
 accuracy issues when projection contact is used.  Switch to other       
 contact detection options or you may use the CNCHECK,ADJUST/MORPH       
 command to move the contact nodes towards the target surface.

 

Here is the link for the solution information doc.

https://drive.google.com/file/d/1P6lDCda0rvN9M4q2DAzZ8vly9_XL4spW/view?usp=sharing

Thanks in advance

Rupa