Newtonian Fluid
The fluids which exhibit constant viscosity under constant temperature and pressure conditions are called Newtonian Fluids. Viscosity is the resistance to flow that any fluid exhibits and in the case of Newtonian fluids, it varies only with changes in pressure or temperature. For Newtonian fluids, viscosity is a ratio of shear stress and shear rate. Light oil, water, salt water, sugar solution, glycerin, air, and other gases are examples of Newtonian fluids. Drilling fluid is not a Newtonian fluid.