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Old   March 16, 2021, 12:02
Default Force / Pressure trace
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G Grewal
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Hi Reef3D Developers,


Thank you for setting up this forum. I have been stalking the website over the last few years hoping for a place to ask questions.


Is there a way to calculate Forces/ pressures on a patch wrt time in reef3d? Also how would you do this with a floating body? Do you setup a stl with patches for the floating body or can mutiple stl files act as a single body?


Thanks in advance.
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Old   March 16, 2021, 12:38
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Arun Kamath
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While I have not tried this, you could apply the force calculation box only for the part of the solid that you want the force to be calculated for.

In the case of floating bodies, currently force calculation is global.
Multiple floating bodies is possible now, but we still have some testing ongoing, before release to the master branch.

That said, I am curious as to what your application is, that requires pressures over patches only? If you want to evaluate the kinematics only for the wetted surface of the object, then REEF3D::FNPF that uses the sigma-grid does this automatically without the need to define patches.
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Old   March 16, 2021, 17:32
Default Multiple Solids
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Thanks for posting the first question in the forum . Right now, the option is that multiple solids can generate one rigid body as well a floating body. The assumption is that in case you use STLs, you have the ability to generate the desired geometry in the CAD program of your choice. Do you have a specific application in mind?

The option for multi-body floating objects is implemented, although a collision algorithm is not in place yet.
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Old   March 16, 2021, 18:03
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Thank you Arun and Hans,


I wanted to validate the code by recreating the cylinder slam impact paper [1]. I have equivalent validation for Openfoam. The cylinder is split up into patches over which the force is measure and point probes at multiple angles over the circumference.


Another application I would like patches for is measuring wave impact forces / pressure contours on panels located on the hull of a floating vessel. This would also allow the pressures to be transferred over to FE for structural analysis. In Openfoam the 6DOF body can be made up of multiple patches. This allows for the forces / pressures to be measured and plot separately for the patches.



An application the FNPF solver can help with is whipping where if the force can be split up into bins [2](equally sized sections along an axis). Then we can transfer the loads to a beam model of a ship every time step allowing for quick Fluid structure interaction.



Thanks again for the quick replies.



[1] http://www.wumtia.soton.ac.uk/sites/.../files/440.pdf
[2] https://www.openfoam.com/documentati...es-forces.html
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Old   March 17, 2021, 08:35
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You could use either point probes (P61) or line probes (P62) to get the pressure in desired locations. Then the local force can be calculated from this or it can be used as input for an FE solver.
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