[ESPResSo-users] unstable solution flow profile

[Wink, Markus]

Dear all,

 

while doing simulations on the flow profile in a slit structure, I have found out that the velocity profile as a function of the grid size becomes unstable. For example, if I choose a width of 50 microns, a force density of 64000N/m^3 and a dynamic viscosity of 0.000125 kg/(ms), the LB-nodes near the maximum velocity starts oscillating and the profile collapses, when the grid size is set to 1. When I start a simulation using a grid size of 0.5, the solution is stable.

 

I was wondering, why that is the case. I mean, what is the physical reason for that and why does it happen near the maximum? I mean, I can deal with that problem, but I am really curios to know, what the reason is. Attached you will find the two flow profiles.

 

Thanks a lot.

 

Greetings

 

Markus

 

stable_unstable.png
Description: stable_unstable.png