👉 A momentum fluid, also known as a viscous fluid or a Newtonian fluid, is a type of fluid whose viscosity remains constant regardless of the applied shear stress or rate of deformation. Unlike gases, which can become less dense under high pressure, momentum fluids maintain a consistent internal friction that resists flow. This property makes them crucial in various physical phenomena, including fluid dynamics, heat transfer, and the behavior of liquids in pipes. Examples include water, air, and oils, where the momentum (or shear) stress is directly proportional to the velocity gradient, as described by Newton's law of viscosity. This characteristic simplifies many fluid mechanics problems and is fundamental in understanding how momentum is conserved and transferred within these fluids.
