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Velocity Dependent Boundary Load

Posted Oct 11, 2017, 3:20 p.m. EDT Structural & Acoustics, Acoustics & Vibrations, Parameters, Variables, & Functions Version 5.2a 4 Replies

Brandon Murray
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Hi all, I'm trying to apply a boundary load (F/area) in the solid mechanics module where the load would look like: T(Pascals)=-C(Pas/m)V(m/s) where T is the Force/area, C is some constant, and V is the velocity of the boundary. I'm working with frequency domain and eigenfrequency studies. I know both the velocity only acts in the x direction in a 2D example. The velocity comes from piezoelectric shearing.

Using the Boundary Load->Load type: Load defined as force per unit area->Fa: user definied: -Csolid.u_tX or -Csolid.uAmptX seem to work as expected. uAmp gives me an unknown variable error, and utX doesn't seem to make a theoretical prediction based on the calculated velocity. I get a load with half the period of the velocity.

Is there a good way to apply a boundary load using the velocity of the boundary? (Using 5.2a)

Thank you,

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4 Replies Last Post Oct 13, 2017, 7:32 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 7 years ago Oct 12, 2017, 2:51 a.m. EDT
Updated: 7 years ago Oct 12, 2017, 2:53 a.m. EDT

Hi Brandon,

The easiest way to accomplish what you want to do is to add a Spring Foundation with no spring stiffness, and only viscous damping.

Regards,

Henrik

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Henrik Sönnerlind
COMSOL
Hi Brandon, The easiest way to accomplish what you want to do is to add a Spring Foundation with no spring stiffness, and only viscous damping. Regards, Henrik
Brandon Murray
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Posted: 7 years ago Oct 12, 2017, 8:53 a.m. EDT

Hi Henrik, Thank you for the quick response. I've never used the spring foundation before but It seems to be working as intended. I'll just need to figure out how the units shake out.

Is there any postprocessing that can be done to view the "damping force" from the constant inserted into Da? For example, I was able to plot solid.FperAreax/y/z on an arrow plot when attemping my previous method.

Best, Brandon

Hi Henrik, Thank you for the quick response. I've never used the spring foundation before but It seems to be working as intended. I'll just need to figure out how the units shake out. Is there any postprocessing that can be done to view the "damping force" from the constant inserted into Da? For example, I was able to plot solid.FperAreax/y/z on an arrow plot when attemping my previous method. Best, Brandon
Henrik Sönnerlind COMSOL Employee

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Posted: 7 years ago Oct 13, 2017, 7:18 a.m. EDT

Sure, you can plot solid.spf1.fdx (/y/z)

Regards, Henrik

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Henrik Sönnerlind
COMSOL
Sure, you can plot solid.spf1.fdx (/y/z) Regards, Henrik
Brandon Murray
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Posted: 7 years ago Oct 13, 2017, 7:32 a.m. EDT

Thank you for the assistance. Hopefully someone else can find this thread useful. Brandon

Thank you for the assistance. Hopefully someone else can find this thread useful. Brandon

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