Hello,
I had a question about the problem statement I’m currently working on.
I’m trying to simulate resin curing respect to time when it’s exposed to source of energy.
Thus, I want my viscosity of fluid to change with time.
Is there a way to make the viscosity of my fluid to change respect to time?
So far, I just defined viscosity using ‘dragfoce’ command using Schiller_Naumann viscosity 0.05.
Any help would be appreciate.
Thanks in advanced!
In MD, viscosity is typically a function of the model, and not a direct input to the simulation without changing the parameters of the potential. It seems like you are looking for a simple model, but you could do a more detailed simulation using fix bond/react and model actual cross-linking of a polymer, which would certainly affect the viscosity over time. Maybe someone else has more ideas.
Thank you for your suggestions.
I’m actually looking for a very simple model, like you mentioned.
I just want the viscosity of my fluid to change with respect to time of my simulation.
I’m wondering if there’s a way to make a user define function to allow the fluid viscosity time-depedent.
There is no dragforce command in LAMMPS (and certainly not “dragfoce”). In fact, there is no mention of that word in the entire LAMMPS documentation. So where did you get this from? Are you using a customized version of LAMMPS?
As @stamoor already stated, viscosity is not an input parameter, but a result of the potential parameters. Many of those can be changed during a run with the fix adapt command (there is a list with available parameters for change).
Setting the viscosity as an external parameter would only apply to implicit solvents or similar and then you would apply a friction term, but note that that would drain energy from your systems, so you would also have to have some source of energy, e.g. some random forces. This will put you into the realm of Langevin dynamics or Brownian dynamics.
In general, it is next to impossible to give any specific advice without knowing more about your model and - for example - seeing an input deck demonstrating what your are trying to run and explanations as to why you chose which parameters and settings to represent which materials etc.