I am only applying an initial velocity to one particle, hence the
total energy of the system is only given by (kinetic + potential elastic).
Look at the two attached figures. The first one (dt_crit) is the
result obtained using the critical time step computed by Pwave in
Yade. The second one (dt_Econst) is obtained decreasing the time step
to get the total energy constant.
I don't think it is an effect of the timestep, but mostly an effect of
the dt/2 shift (smaller with smaller dt). I mean : energy WILL be
constant even with the larger dt if you correct this shift (check in the
previous ods file I sent).
Now I see that the time step influences the solution in terms of
energy and this is just a very little example (so it does not really
quantify anything). However, I have one consideration: does this mean
that we are mainly dealing with non conservative systems in our dem
simulations? Is this the right way to compute the total energy?
Your way is correct. IMO, energy will be approximately constant if you
correct the dt/2 shift in kinE. Without this correction, energy will
still be constant in all quasi-static processes.
Cheers.
Bruno
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