NVT/NVE Ensemble for flow system

Dear LAMMPS Users,

In order to realize the poiseuille flow, generally, we build a system including fluids and medium. In most cases, we only fix the medium and impose NVT ensemble to fluids. Herein, I am confused about the choice of ensemble for flexible system.

Basically we have two choices:

1: Just give NVT ensemble to the moving part, and modify the temperature by water temperature excluding the moving direction, by the following command

compute Twater water temp/partial 1 1 0

fix 1 movepart nvt temp 300.0 300.0 100.0

fix_modify 1 temp Twater

  1. Give NVT ensemble to the flexible underlying medium to control the temperature, and meanwhile give NVE to fluids .

fix 1 surface nvt temp 300.0 300.0 100.0

fix 2 water nve

which one should be better and physically reasonable?

And I have tested these two cases, it seems that the outcome temperature from the second one gives better results.

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Hope to hear from soon. Thank you very much.

Best Regards,

Timmy