Which fluid property primarily affects shear losses and flow resistance?

Which fluid property primarily affects shear losses and flow resistance?

• A. Density
• B. Viscosity
• C. Compressibility
• D. Temperature

Answer: (B)

Viscosity is the property that directly governs how fluids resist shear between layers. When a fluid flows, adjacent layers slide past one another, and internal friction acts to oppose that motion. This friction is the shear stress, which for many fluids is proportional to the velocity gradient and the fluid’s viscosity. So, higher viscosity means larger shear stresses for the same velocity profile, leading to greater energy dissipation and greater flow resistance. Density mainly affects inertia and how the flow responds to acceleration, not the friction between layers. Compressibility matters more in high-speed or gas flows where density changes are significant. Temperature influences both viscosity and density, but it’s viscosity itself that sets the rate of shear losses and overall resistance to flow.

Viscosity is the property that directly governs how fluids resist shear between layers. When a fluid flows, adjacent layers slide past one another, and internal friction acts to oppose that motion. This friction is the shear stress, which for many fluids is proportional to the velocity gradient and the fluid’s viscosity. So, higher viscosity means larger shear stresses for the same velocity profile, leading to greater energy dissipation and greater flow resistance.

Density mainly affects inertia and how the flow responds to acceleration, not the friction between layers. Compressibility matters more in high-speed or gas flows where density changes are significant. Temperature influences both viscosity and density, but it’s viscosity itself that sets the rate of shear losses and overall resistance to flow.