Water hammer depends on the fluid’s compressibility particularly when there are sudden changes in which parameter?

Water hammer depends on the fluid’s compressibility particularly when there are sudden changes in which parameter?

• A. Color
• B. Temperature
• C. Pressure
• D. Viscosity

Answer: (D)

Water hammer is a transient surge in pressure caused by a rapid change in the liquid’s flow velocity in a pipe. The speed at which the resulting pressure disturbance travels is set by the fluid’s compressibility (and the pipe’s stiffness); a more compressible fluid or a stiffer pipe changes the wave speed and, together with the rate of velocity change, determines how large the pressure rise will be. In the standard relation for surge pressure, the peak pressure is proportional to the change in velocity and to the wave speed that depends on compressibility, so the impulse that creates the surge comes from a sudden change in velocity. Viscosity, on the other hand, mainly affects how the pressure transient is damped as it propagates. Higher viscosity tends to dissipate energy more rapidly, smoothing and reducing the peak of the surge over distance and time. So while compressibility and the sudden velocity change govern the initial surge, viscosity governs the subsequent damping.

Water hammer is a transient surge in pressure caused by a rapid change in the liquid’s flow velocity in a pipe. The speed at which the resulting pressure disturbance travels is set by the fluid’s compressibility (and the pipe’s stiffness); a more compressible fluid or a stiffer pipe changes the wave speed and, together with the rate of velocity change, determines how large the pressure rise will be. In the standard relation for surge pressure, the peak pressure is proportional to the change in velocity and to the wave speed that depends on compressibility, so the impulse that creates the surge comes from a sudden change in velocity.

Viscosity, on the other hand, mainly affects how the pressure transient is damped as it propagates. Higher viscosity tends to dissipate energy more rapidly, smoothing and reducing the peak of the surge over distance and time. So while compressibility and the sudden velocity change govern the initial surge, viscosity governs the subsequent damping.