👉 In the context of thermodynamics and fluid mechanics, the fluid applicable in a given scenario is typically classified as either a Newtonian or a non-Newtonian fluid, depending on its behavior under stress. A Newtonian fluid is one whose viscosity remains constant regardless of the applied shear stress, meaning it flows at a steady rate and its resistance to flow does not change with force. Examples include water, air, and most simple oils. On the other hand, a non-Newtonian fluid's viscosity changes with applied stress; it can become more or less viscous depending on the force or shear rate applied. Examples include ketchup, blood, and certain polymer solutions. Understanding whether a fluid is Newtonian or non-Newtonian is crucial for predicting its behavior in various applications, from industrial processes to biological systems.
