What term describes the measure of a hydraulic fluid's resistance to flow?

The term that describes the measure of a hydraulic fluid's resistance to flow is viscosity. Viscosity is a critical property of fluids that determines how easily they can move through a system. In hydraulic systems, higher viscosity fluids exhibit greater resistance to flow, which can impact the efficiency and performance of hydraulic operations.

For instance, a hydraulic fluid with low viscosity will flow easily and require less energy to pump, while high-viscosity fluids can lead to increased friction and energy loss. Understanding viscosity is crucial for selecting appropriate fluids for specific applications in hydraulic systems to ensure optimal performance and prevent issues such as overheating or insufficient lubrication.

While density refers to the mass of a fluid per unit volume, compressibility describes how much a fluid can change in volume under pressure, and fluid dynamics is the study of how fluids behave in motion, none of these terms specifically relate to the resistance of fluid flow as directly as viscosity does. Therefore, viscosity is the correct term associated with the flow resistance in hydraulic fluids.