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How to define that mathematical expression?

Francesc-Xavier Borras

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Hi,

I get a pressure on a segment shaped surface using a "physic". In the real life, this surface is spinning really fast, I would like to use this pressure field (mod1.pf) to achive an axisymmetric one, and then obtain a more accurate displacement on the surface.

My idea is to use a mathematical expression to obtain an axisymmetric pressure profile taking the maximum pressure for each radius of the one I already have.

maxop1(mod1.pf) - I do not know how to input that I want the maximum for every radius,not the maximum pressure of the surface.

I will post an example if it is not clear enough.

Thanks in advance

PS. Simplified: I have an half sphere pressure distribution and I would like to obtain a half toroidal shaped one.

2 Replies Last Post 22 avr. 2012, 14:06 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 22 avr. 2012, 08:15 UTC−4
Hi

I do not believe I fully catch you, but if your object is "spinning" it sees a body load from the acceleration, that you can add like that (see the model library optimising spinning flywheel. Or ad a Body load with a sys2.r force of the type sys2.r*omega^2

where omega is the constant rotation speed in turns per sec, and "sys2." is a Definitions Coordinates" cylindrical coordiante set up on the rotation axis

In this way your object is not moving w.r.t. your x,y,z coordiante frame but the you rotate virtually your coordinate frame

--
Good luck
Ivar
Hi I do not believe I fully catch you, but if your object is "spinning" it sees a body load from the acceleration, that you can add like that (see the model library optimising spinning flywheel. Or ad a Body load with a sys2.r force of the type sys2.r*omega^2 where omega is the constant rotation speed in turns per sec, and "sys2." is a Definitions Coordinates" cylindrical coordiante set up on the rotation axis In this way your object is not moving w.r.t. your x,y,z coordiante frame but the you rotate virtually your coordinate frame -- Good luck Ivar

Francesc-Xavier Borras

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Posted: 1 decade ago 22 avr. 2012, 14:06 UTC−4
Hi Ivar,

Thanks for the explanation. Sorry because I think I explained myself really bad. I try again with a picture:

I have a segment shaped model. It represents the rotor(mod2). I already achieved before the pressure applied in the stator (in another model(mod1)):

Pressure applied in a segment of the stator (mod1.pf).

Since now I was applying this pressure to the rotor surface(mod2) as a Boundary Load (the snap I attached).

Then I realized that the deformation of the rotor(mod2) would be more accurate if ithe load applied was axysimmeric.

I attach a snap of the pressure I obtained from the stator(mod1.pf) applied in the rotor(mod2).

I would like it to be axisymmetric:

- To be applied in all the segment.
- Taking the maximum pressure for each radius and aplying it to all the segment radius. So no edge effects, I would like the load applied snap I attached to have the same pressure at the same distance to the centre. p = f(radius).

I hope it is clear enough. My apologises for any inconvenience.
Do not hesitate to ask me for more snaps or infromation.



Hi Ivar, Thanks for the explanation. Sorry because I think I explained myself really bad. I try again with a picture: I have a segment shaped model. It represents the rotor(mod2). I already achieved before the pressure applied in the stator (in another model(mod1)): Pressure applied in a segment of the stator (mod1.pf). Since now I was applying this pressure to the rotor surface(mod2) as a Boundary Load (the snap I attached). Then I realized that the deformation of the rotor(mod2) would be more accurate if ithe load applied was axysimmeric. I attach a snap of the pressure I obtained from the stator(mod1.pf) applied in the rotor(mod2). I would like it to be axisymmetric: - To be applied in all the segment. - Taking the maximum pressure for each radius and aplying it to all the segment radius. So no edge effects, I would like the load applied snap I attached to have the same pressure at the same distance to the centre. p = f(radius). I hope it is clear enough. My apologises for any inconvenience. Do not hesitate to ask me for more snaps or infromation.

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