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paulakash24 / LUMA_TEST

This repository is solely for testing purposes. The original repository belongs to cfdemons and can be accessed through https://github.com/cfdemons/LUMA . This is used as a testing platfrom only.
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Flexible Pitching #1

Open Alexg2991 opened 1 year ago

Alexg2991 commented 1 year ago

Hi Paulakash

I was looking at the Luma directory and saw your issue regarding the prescribed motion. I wanted to simulate a flexible filament while in pitching motion. I can see you have already added the rigid form to the code. I saw some of the videos, that all seem rigid cases. Have you also added the flexible form?

I tried to give y motion to a flexible filament but the output velocity changed to NaN after a couple of iterations

Kind regards

paulakash24 commented 1 year ago

Hi Alex,

I was able to give prescribed motion to rigid bodies. But I wasn't able to give prescribed motion to a flexible filament. Some of my team members worked to give heaving motion to the leading edge of the flexible filament (only to the first IB marker; the rest of the body will follow) but we were unable to validate the results. The work did not continue due to lack of resources and support.

Please let me know if need to know any further.

Thanks and Regards Akash

Alexg2991 commented 1 year ago

Hi Paulakash,

Thank you very much for your answer

Given that LBM is a finite difference scheme in nature I believe in the case of flexible filament the mass conservation needs to be explicitly imposed so the energy does not dissipate and the density population does not go out of bounds due to dynamic motion. I haven't gone through the code, but do you have the version that your teammates worked on so I can check the problem?

Also, do you have the definition and input files for any FSI validation cases so I can make a comparison? especially the rigid hovering (pitching and or heaving) motions?

Kind regards

paulakash24 commented 1 year ago

Hi Alex,

Sorry for the delayed response.

For FSI validation I used the case of Huang et. al 2018 (paper available in respective folder in the link below). The prescribed motion for rigid filaments (both pitching and heaving) were not validated. Also, I can share the source files for heaving motion of a flexible filament, which was attempted by one of my teammates.

The google link below contains source files of all the cases mentioned above.

https://drive.google.com/drive/folders/1TpBk_p5yfZE0BBZyAg5GLBM3fu-wJS3e?usp=sharing

Please let me know if you need anything else.

Thanks and regards Akash

paulakash24 commented 11 months ago

Hi Alex,

I hope you found the resources useful.

Just curious to know if you had found any breakthrough. Feel free to share.

Thanks and regards Akash

Alexg2991 commented 8 months ago

Hi Paulakash,

I'm sorry for not getting back to you sooner.

Unfortunately, the code is not stable for this kind of simulation. I have worked on three validation cases for flexible cases with prescribed motion but couldn't match the results (or even flow behavior). I have switched to a Navier Stokes FSI code using dynamic mesh instead of an Immersed Boundary. I can see they have coupled the code with another solver for heat transfer. currently working to see if we can validate that or not? Im also hoping to run a 3D validation case with the solver and see how reliable it is.

paulakash24 commented 7 months ago

Hi Alex, No issues. I also feel the same. And I am looking for a NS-conforming mesh based FSI solver for a study. I would like to know about the solver that are available for such studies. It would be great if you could send me an email on apaul818@gmail.com so that we talk further. Thanks

Alexg2991 commented 3 months ago

Hi Alex,

Sorry for the delayed response.

For FSI validation I used the case of Huang et. al 2018 (paper available in respective folder in the link below). The prescribed motion for rigid filaments (both pitching and heaving) were not validated. Also, I can share the source files for heaving motion of a flexible filament, which was attempted by one of my teammates.

The google link below contains source files of all the cases mentioned above.

https://drive.google.com/drive/folders/1TpBk_p5yfZE0BBZyAg5GLBM3fu-wJS3e?usp=sharing

Please let me know if you need anything else.

Thanks and regards Akash

Hi Paulakash,

I think I have finally solved the problem with flexible heaving and pitching cases. the only thing is that it requires an extremely fine mesh. unfortunately, the code has a bug in which when you use both parallelization and multiblock, it cannot read the geometry. do you have a solution for that? I need to set up a series of cases with very fine mesh and run the validation to make sure it works.

paulakash24 commented 3 months ago

Hi Alex,

I remember that I also faced this same issue while using parallelization and multi-block refinement at the same time. Unfortunately, I could not find a solution for that and used 3 different grid sizes for grid independence studies.

It is good to know that you have been successful in running the flexible heaving and pitching cases. Have you been able to validate those?

Interested to see your results.

Thanks & Regards Akash

Alexg2991 commented 2 months ago

Hi Alex,

I remember that I also faced this same issue while using parallelization and multi-block refinement at the same time. Unfortunately, I could not find a solution for that and used 3 different grid sizes for grid independence studies.

It is good to know that you have been successful in running the flexible heaving and pitching cases. Have you been able to validate those?

Interested to see your results.

Thanks & Regards Akash

Hi Akash,

I have validated the flexible heaving and pitching with a different LBM open-source solver. the solution was in the boundary conditions. for this case, the Fluid boundary condition has to be used and the flow has to be driven by body force, not the inlet velocity. I'm trying to do the same thing in LUMA but I ran into problems using the Gravity function in flexible and motion cases. I saw you raised this issue before in "Simulating Flexible Filaments with gravity ON #21". were you able to solve this?

I want to validate LUMA for this case because the implicit coupling and the immersed boundary method used in this code is much more reliable for low-density cases than the other code.

if you have solved the issue of using the body force (gravity) with flexible or even rigid heaving and pitching please let me know as I believe this can solve the issue with validation. the only thing is that the gravity force has to be fixed in a way that the same flow rate is achieved.