Hello every one...
i used Hertz contact model in my simulations in following form:
F=(Kn δn- γn Vn ) + (Kt δt- γt Vt )
The first term represents the normal force between two particles while the second term represents the tangential force. Here Vn and Vt are normal and tangential components of the relative velocity. The coefficients K_n, K_t, γ_n, and γ_t are calculated from the material properties.
As per my supervisor, the terms for normal and tangential forces are added as scalars. The first two terms contribute to the normal force Fn and the other two terms contribute to the tangential force. These two point in two mutually perpendicular directions and hence can not be added as scalars.
He asked me to write this equation in vector form, by using arrow as over bar.
Now i am confused where to put arrows ??? i mean which term need arrows as over bar.??
Kindly if someone can guide me regrading the same...
Thanks everyone
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mschramm | Thu, 08/13/2020 - 23:19
scalars and vectors
K_n, gamma_n, K_t, and gamma_t are scalars and delta_n, Vn, delta_t, and Vt are vectors.
so (I prefer to use bold to signify a vector),
F=(Kn δn- γn Vn ) + (Kt δt- γt Vt )
Gulniamat | Wed, 08/19/2020 - 17:17
Hertz model
Many thanks sir...
Sir as I am new to LIGGGHTs therefore, I don't have enough knowledge about the use of models. I told my supervisor that I used above Hertz contact model in my simulation study. Now he told me that the terms for normal and tangential forces are added as scalars. The first two terms contribute to the normal force Fn and the other two terms contribute to the tangential force. These two point in two mutually perpendicular directions and hence can not be added as scalars. Now he asked me to at least correctly write the equation used in the simulation. Now I am confused, as same form of Hertz model is given in online documentation ( LIGGGHTS V3.X). sir kindly guide me how I can I answer him ??? So that he may be satisfied.
Again thanks for facilitation
mschramm | Wed, 08/19/2020 - 19:15
normal and tangential in x,y, and z direction
When you have two particle come into contact with each other, they exert forces and torques onto each other. These normal and tangential forces and torques can be further broken down into their coordinate forces.
So if we look at the sum of forces in the x-direction
F[0] = Fn[0] + Ft[0]
You can see this further broken down in the source code.
https://github.com/CFDEMproject/LIGGGHTS-PUBLIC/blob/master/src/normal_m...