Yade

How to get P-wave and S-wave velocity

Asked by Leonard

Hi,

I'd like to ask that how to get the P-wave velocity and Shear wave velocity in Yade for a DEM soil model?

According to [1], in which it gets timestep accoring to the velocity of P-Wave propagation, so I guess there is already an function that can directly get the P-Wave velocity, but I didn't find it.

For the Shear wave velocity, do you have any suggestions to get it?

Thanks!

Leonard

[1]https://yade-dev.gitlab.io/trunk/yade.polyhedra_utils.html?highlight=pwave#yade._polyhedra_utils.PWaveTimeStep

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Jérôme Duriez (jduriez) said : 		#1

I think what is usually coined in the doc as P-Wave velocity is
(b.mat.young / b.mat.density)**0.5 # b a body with a material having these young and density attributes -- most of them.

Whether (b.mat.young / b.mat.density)**0.5 actually is a elastic wave velocity in a packing including bodies with these velocities is another question, in my opinion (and the answer would be no), but this is part of the classical confusion about these "young" parameter..

As for the S-wave velocity, it's kind of the same: the only way I see to measure it is to actually simulate a S wave and to measure its speed.

(Note that in the particular case of your link, the doc is even more unfortunate in my opinion -- on my TODO list by the way.. -- since PolyhedraMat.young may not be a stress-like quantity in Pa)

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Jérôme Duriez (jduriez) said : 		#2

The above should read

> in a packing including bodies with these *parameters*

Sorry

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Bruno Chareyre (bruno-chareyre) said : 		#3

Hi,

PWave velocity is (bulk modulus /density)**0.5 with "modulus" and "density" defined at the macroscale.

For density it is simply mat.density * (1-porosity). For the modulus, you can evaluate it with a static loading (uniaxial compression).
I would discourage trying to actually simulate a wave propagation, it is particularly complex and error-prone.
Bruno

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Leonard (z2521899293) said : 		#4

Thanks Jérôme and Bruno!