Fluid Mechanics & Fluid Properties
Molecular momentum exchange
Particles of one layer jumps into the other adjacent layer and vice versa.
As a result the particles in the upper layer consists of some slower particles and in the lower layer we have some fast moving particles. So, the net velocity of upper layer decreases and lower layer increases.
Cohesion force of attraction
Particle of a layer attracts the particles of other adjacent layer.
As a result net force in the backward direction for upper later and forward direction for lower layer. So, the net velocity of upper layer decreases and lower layer increases.
