[ESPResSo-users] WG: gravitational force on a rigid object with virtual sites and the meaning of the mass

[Holst, Lena]

Hello,

 

I want to run an simulation with an rigid object, that consists of virtual sites.

I want to apply a gravitational force on this object.

Do I have to apply the gravitational force only on the non-virtual particle, on the virtual, too or only on the virtual.

In the userguide I have read, that  forces accumulated on a virtual site are distributed back to the non-virtual site.

Because of that, I thought that I have to apply the gravitational force only on the virtual particles. If I have 67 virtual particles, I have to divide the force with 67, I think. I have try that, but get the error message that the particle is out of range. If I apply lower forces, I did not get this error message, but I apply a wrong force.

 

Another question I have about the choice of the mass m that is calibrate together with the frictional coefficient.

I thought I am able to choice any mass m and adjust the frictional coefficient as long as the theoretical velocity of the object is nearly the same as the simulated. That has the result that this mass does not present the mass of the object. The mass of the object I set through the choice of the theoretical course of the velocity with time. Is that the fact?

 

At first I thought, the gravitational force is give through the mass, that I have set trough the choice of the theoretical course of the velocity by calibration. But now I think it could be, that the force is give through the other mass m. Could it be?

 

I hope I have write good enough, that you can understand me.

 

Kind regards and a lot of thank,

Lena Holst

 

Lena Holst

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