The ideal flow of any fluid must satisfy the continuity equation, which represents the law of conservation of mass.
Pascal's law states that the pressure at a point in a fluid at rest is the same in all directions. Viscosity is a property of a fluid by virtue of which it offers resistance to flow, and
Newton's law of viscosity relates shear stress to shear strain.
The boundary layer theory describes the thin layer close to the wall in a flow field where viscous stresses are prominent.
