fluid with constant average velocity

Dear all,

I want to model a fluid by SPH method to have constant average velocity in one direction ( i.e. x dim) during simulation time. how can i do it?
velocity command sets an initial condition on velocity. but the fluid due to viscosity will be stationary quickly.


Perhaps check the archives. This has come up on the mail-list numerous times, for example in the case of Poiseuille flow.

Thank you dear Eric,

I want to have free surface on top of the fluid and fixed floor. In Poiseuille flow was used aveforce on fluid groups NOT average velocity. Do i use aveforce command then adjust the fx parameter to determine desired average velocity?

If you have a free surface, how would you obtain a constant mean velocity (in the physical situation)? Gravity, no?

I think there is no problem in physical situation. Suppose there is a gravity acceleration in -y (Down) direction and fluid moves to +x (Right) direction. in the x direction BC is periodic.

If you want better feedback, you’re going to have to convince people that its necessary. Right now its still unclear what you want to do.

To answer your question on setting fx question, Its clear from the documentation that you can control fix addforce with equal and per-atom variables, why not utilize compute reduce to set up a simple control method. I’d still advocate for using a constant force, unless its clear that you need otherwise.