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prescibed displacement

Posted 28.05.2012, 21:37 GMT-4 RF & Microwave Engineering, Acoustics & Vibrations, Geometry, Materials, Structural Mechanics 9 Replies

Joquin Santos
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Hey

how to create a point that oscillates (up and down) with a determined frequency?
(so that it will generate a wave propagating along a plate)

Btw, I'm using acoustic-structure interaction module, is the correct one to use for this application?
(and I'm using 2D, square)
9 Replies Last Post 21.10.2013, 17:28 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 29.05.2012, 04:32 GMT-4
Hi

here is an example its for 4.2a


But normally one should not use "point" loads as these leads to "singularities", rather boundary loads

For a plate you could also use a Pressure boundary load, from tha acoustic solution

--
Good luck
Ivar
Hi here is an example its for 4.2a But normally one should not use "point" loads as these leads to "singularities", rather boundary loads For a plate you could also use a Pressure boundary load, from tha acoustic solution -- Good luck Ivar
Joquin Santos
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Posted: 1 decade ago 29.05.2012, 16:47 GMT-4
I can't open it
my pc almost crashes

maybe if you tell me the main steps

thanks Ivar
I can't open it my pc almost crashes maybe if you tell me the main steps thanks Ivar
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30.05.2012, 01:46 GMT-4
Hi

well I do not have any earlier version than 4.2a up running, but here is a screen view, the point load is not the best way, the better is a boundary load on the tip edge, but in this case you get the same results

--
Good luck
Ivar
Hi well I do not have any earlier version than 4.2a up running, but here is a screen view, the point load is not the best way, the better is a boundary load on the tip edge, but in this case you get the same results -- Good luck Ivar
Joquin Santos
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Posted: 1 decade ago 30.05.2012, 02:58 GMT-4
Why you use solid mechanics instead of Plate?
I want to do the application of the waves in thin plates, does it make any difference using Solid Mechanics or Plate ?

Thanks
Why you use solid mechanics instead of Plate? I want to do the application of the waves in thin plates, does it make any difference using Solid Mechanics or Plate ? Thanks
Joquin Santos
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Posted: 1 decade ago 30.05.2012, 03:32 GMT-4
That isn't working because I want to apply the force in the z direction, and like that it only allows to me to apply either in x or y direction... :(
That isn't working because I want to apply the force in the z direction, and like that it only allows to me to apply either in x or y direction... :(
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30.05.2012, 08:57 GMT-4
Hi

pls be more specific then, I did not catch the 3D issue from your previous lines, then apply my model to 3D,
And as you say: a X-Y shell could do with Z displacement, the principle for the model remain

--
Good luck
Ivar
Hi pls be more specific then, I did not catch the 3D issue from your previous lines, then apply my model to 3D, And as you say: a X-Y shell could do with Z displacement, the principle for the model remain -- Good luck Ivar
Joquin Santos
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Posted: 1 decade ago 30.05.2012, 13:54 GMT-4
ok, I was just wondering

by the way, how to put the point source oscilating with a specific frequency?
ok, I was just wondering by the way, how to put the point source oscilating with a specific frequency?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30.05.2012, 14:54 GMT-4
Hi

If you check the forum this has been discussed several times:

are you interested in the transients or in a steady state value ?

1) for transient choose the time series solver, add the force as F0*sin(2*pi*freq*t) and solve, then decide if you want to include the inertial terms or only the quasi static ones, usea fine time step to resolve your sinus periode, and set the Time Stepping tab in the lower level solver node to "intermediate" as "free" will mostly skip over your oscillations

2) for a harmonic development (if applicable to your physics) then choose the Frequency Domain solver, define the frequency or frequency range in the solver settings, and the force amplitude F0 as the point or better boundary load. You miht add a phase info either as a phasor F0*exp(i*phase_in_rad) or by a explicit phase field, or subnode, if there

--
Good luck
Ivar
Hi If you check the forum this has been discussed several times: are you interested in the transients or in a steady state value ? 1) for transient choose the time series solver, add the force as F0*sin(2*pi*freq*t) and solve, then decide if you want to include the inertial terms or only the quasi static ones, usea fine time step to resolve your sinus periode, and set the Time Stepping tab in the lower level solver node to "intermediate" as "free" will mostly skip over your oscillations 2) for a harmonic development (if applicable to your physics) then choose the Frequency Domain solver, define the frequency or frequency range in the solver settings, and the force amplitude F0 as the point or better boundary load. You miht add a phase info either as a phasor F0*exp(i*phase_in_rad) or by a explicit phase field, or subnode, if there -- Good luck Ivar
yuanyuan liu
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Posted: 1 decade ago 21.10.2013, 17:28 GMT-4
Dear Ivar,

Sorry to bother you, but i find your model almost fits my problem. "Scientists and engineers that seek to understand elastic wave propagation in geological structures typically consider the generic problem of a seismic wave that is generated at a source, propagates through a media, and is measured at a receiver." describes my problem perfectly. In my case, the media contains two different isotropic material. What i want is the waveforms at different receivers. I am wondering if you can help me with this. I assume there is a boundary load on the top boundary of material 1. Please see my attached geometry file. Thank you so much.



Hi

here is an example its for 4.2a


But normally one should not use "point" loads as these leads to "singularities", rather boundary loads

For a plate you could also use a Pressure boundary load, from tha acoustic solution

--
Good luck
Ivar

Dear Ivar, Sorry to bother you, but i find your model almost fits my problem. "Scientists and engineers that seek to understand elastic wave propagation in geological structures typically consider the generic problem of a seismic wave that is generated at a source, propagates through a media, and is measured at a receiver." describes my problem perfectly. In my case, the media contains two different isotropic material. What i want is the waveforms at different receivers. I am wondering if you can help me with this. I assume there is a boundary load on the top boundary of material 1. Please see my attached geometry file. Thank you so much. [QUOTE] Hi here is an example its for 4.2a But normally one should not use "point" loads as these leads to "singularities", rather boundary loads For a plate you could also use a Pressure boundary load, from tha acoustic solution -- Good luck Ivar [/QUOTE]

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