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Spinning Disk Trick

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Hello guys!

My name is Domien and I'm new here :)
I'm a physics student at the University of Antwerp, Belgium. I'm currently working on my Bachelor's thesis.

I'm trying to model a Spinning Disk with a hole in it, just like in this fun video: www.youtube.com/watch?v=h0SZZTBQmEs
It is my goal to learn more about this weird effect by modeling the spinning disk in COMSOL. However, I am new to COMSOL and there is nobody at the University who can help me with it. That's why I'm asking you guys for help :)

I have already succeeded in modeling the disk itself and a rectangular cuboid, which serves as the floor. Things yet to be done: add gravity to the disk, add friction between the objects, make it a time-dependent study and set initial velocity and position.

Can any of you awesome people help me with this? :D

Thanks!

Domien

PS: When I'm at the University on monday, I will be able to upload my latest file.

1 Reply Last Post 17 mars 2013, 11:07 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 17 mars 2013, 11:07 UTC−4
Hi

have you checked the moel library for the rotating disck (not sure exact name just now ;) you add gravity as body load g_const*solid.rho in [kg/m^3*(m/(s^2)]=[N/m^3] but if your disk is spining by "n" rpm (rotations per mintes) yoi can add this by using a used defined cylindrical coordinate system a second body force in the radial direction of (2*pi*n/60)^2*r

where 60 is the conversion [s/min] and r is typically sqt(x^2+y^2) or sys2.r in your coordinate system (note it might be 3 or 4 ...) this applises for a Z direction axis ;)

In this way your geometry is fixed, but yourreferntial is rotating (action - reaction) ...

--
Good luck
Ivar
Hi have you checked the moel library for the rotating disck (not sure exact name just now ;) you add gravity as body load g_const*solid.rho in [kg/m^3*(m/(s^2)]=[N/m^3] but if your disk is spining by "n" rpm (rotations per mintes) yoi can add this by using a used defined cylindrical coordinate system a second body force in the radial direction of (2*pi*n/60)^2*r where 60 is the conversion [s/min] and r is typically sqt(x^2+y^2) or sys2.r in your coordinate system (note it might be 3 or 4 ...) this applises for a Z direction axis ;) In this way your geometry is fixed, but yourreferntial is rotating (action - reaction) ... -- Good luck Ivar

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