The Navier-Stokes equations represent the flow of a fluid with friction. They consist of the following conservation equations:
Conservation of mass (second line):
div u=0
Conservation of momentum (first line)
−μΔu+(u⋅∇)u+∇p=f
Conservation of energy (probably, in the third line, but I don't know the nomenclature):
u∣Γ=0.
