Simple way to implement contact duration

Hi All,

I want to extract information about contact duration and maybe I have found a really simple way to do it.

In cohesion_model_easo_capillary_viscous.h there is a history_value "contflag" that is used to understand if two particles have been in contact, such that the capillary force is created only after the contact occurs.

The contflag is set to 1 in case of contact, then set to 0 when the liquid bridge is broken. One can increment the contflag rather than setting to 1 and the condition still works.

contflag[0] = contflag[0] + 0.0;

In this way contflag carries the information of "how many time-steps the contact lasts for". Remember that liquid bridge force is active when there is overlap as well.
I have tested it for two particle collision and it works.

If the history_value is added into normal contact model it might work at the same way. It might be a good idea to have this feature in LIGGGHTS as the contact duration is really useful to study clustering, agglomeration, heat transfer etc...

My first question is:
Do you see any problem with this idea?

My second question:
How can I export the history value "contflag" using the dump local command?

I just want to remind you that the dump local command has some issues when used together with cohesion_model_*_capillary_viscous.
see http://www.cfdem.com/forums/error-when-compute-pairgranlocal-capillary-m...

Thank you.
Regards,
Giuseppe