Particle trajectory. it seems to be same velocity regardless of size of particle.

Hi. I'm trying to simulate particle tracking in the fluid(water)
and my situation is laminar flow.
And I applied Drag force, but the particle is moving to same direction.
I think the particle shows different movement as diameter, because Drag force depends on diameter of particle.
Even though comsol calculated Drag force which is related with diameter of particle, the velocity is the same.
why?

For example, there are 1um particle and 10um particle.
Drag force was calculated as 1N and 10N. it is obviously as equation.
However the velocity is the same. so two particles are moving the same.

is anyone why it is occurred?