Viscosity Formula The viscosity of a fluid is defined as the ratio of the shearing stress to the rate of change in velocity (velocity gradient) within the fluid. Viscosity : Definition, Unit & FormulaShear Stress and Shear Rate Two factors that relate to the mathematical formulation of viscosity are shear stress and shear rate. In order to understand the formal definition of viscosity , it is first important to understand the definitions of these quantities. Consider the method of approximating fluid flow as layers of fluid flowing past each other. If we think of a flowing fluid like this, the shear stress is the force pushing one layer across another ... Learn about viscosity , what it means in physics and engineering, and the difference between dynamic and kinematic viscosity measurements. In general, however, the viscosity of a system depends in detail on how the molecules constituting the system interact, and there are no simple but correct formulas for it.
