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PML in structural mechanics

Morten Wollert Nygren

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Is there a way to make a PML in structural mechanics that will match all wavelengths, like the PML in acoustics?

3 Replies Last Post 2010年12月13日 GMT-5 16:28
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2010年11月26日 GMT-5 17:48
Hi

No I do not know about that, but you could try to add some damping on your fixed parts with a boundary force

-k*u -damp*MyLambda

for eigenmodes set MyLambda variable to "lambda" of COMSOL, for frequency sweep try a

myLambda = -i*2*pi*freq

and repeat for v, w ...

however it will make your structure move in all directions

--
Good luck
Ivar
Hi No I do not know about that, but you could try to add some damping on your fixed parts with a boundary force -k*u -damp*MyLambda for eigenmodes set MyLambda variable to "lambda" of COMSOL, for frequency sweep try a myLambda = -i*2*pi*freq and repeat for v, w ... however it will make your structure move in all directions -- Good luck Ivar

Morten Wollert Nygren

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Posted: 1 decade ago 2010年12月13日 GMT-5 10:13
Hi

Could you please elaborate a bit? I don't understand how I should implement this boundary force...

Is this a boundary force?

Hi Could you please elaborate a bit? I don't understand how I should implement this boundary force... Is this a boundary force?

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2010年12月13日 GMT-5 16:28
Hi

first of all I have noticed that there are some PML BC's that appear time to time in the structural (v4) (depends on solver mode and on options installed), but I haven really looked into these as I'm not doing accoustic and have not seen any need to try PML's in structural so far.

What I was also saying is that you have the COMSOL implemented damping parameters (that you migh tune in at a given frequency) but you can also defne a "user" boundary load of the type -w*k[N/m] for a spring load along Z, as well as for an eigenfrequency solver a boundary load of load -w*damping[kg/s]*lambda for a damper (that by adapting the "damping" variable might be critical damping a motion at a given frequency). But dependingon your model I'm not sure its that easy to use these somewhat crudes methods. for a frequency sweep lambda is not defined, but you have "freq", and lambda = -i*2*pi*freq (if I have got that right, pls check carefully ;)

--
Good luck
Ivar
Hi first of all I have noticed that there are some PML BC's that appear time to time in the structural (v4) (depends on solver mode and on options installed), but I haven really looked into these as I'm not doing accoustic and have not seen any need to try PML's in structural so far. What I was also saying is that you have the COMSOL implemented damping parameters (that you migh tune in at a given frequency) but you can also defne a "user" boundary load of the type -w*k[N/m] for a spring load along Z, as well as for an eigenfrequency solver a boundary load of load -w*damping[kg/s]*lambda for a damper (that by adapting the "damping" variable might be critical damping a motion at a given frequency). But dependingon your model I'm not sure its that easy to use these somewhat crudes methods. for a frequency sweep lambda is not defined, but you have "freq", and lambda = -i*2*pi*freq (if I have got that right, pls check carefully ;) -- Good luck Ivar

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