On 2 June 2010 17:06, Bruno Chareyre <[email protected]> wrote:
> Hi Chiara, > > I didn't take time to reply as it would need a long discussion. Keep > looking into MD litterature and you should find questions to your answers, > be it in a formalism that is excessively complex. > I don't agree with your equations below (giving Cundall way). I don't think > anybody ever wrote equation (1). There is a very BIG difference between > vel=... and vel+=...; Cundall is using vel=... where vel is the mean field > velocity. > What do you mean as mean field velocity ? To report exactly from his paper what he wrote in terms of displacement increment : delta_u = delta_u(real_vel) + gradVel*pos*dt; where : delta_u(real_vel) = vel*dt; (vel is from the real particle velocity, hence = a*dt) So the increment of velocity I guess would be given by : delta_v = vel + gradVel*pos; That is why I was writing in my previous post : vel+=vel+gradVel*pos; (I was only missing the vel given by a*dt, but I thought it was implicit) Is this wrong ? IICR, you were writing the same thing in a previous post in this thread, like: if (homotheticCellResize>1) state->vel+=scene->cell->velGrad*state->vel*dt; and now you say that equation vel+=velGrad*vel*dt (1) is wrong. Does not look exactly the same you wrote ? cheers. Chiara
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