What is described as unsteady flow?

• A. Flow parameters change over time
• B. Flow parameters remain constant
• C. Flow is uniform
• D. Depth does not vary

Answer: (A)

Unsteady flow is characterized by changes in flow parameters over time. This means that factors such as velocity, pressure, and flow depth can fluctuate as the flow of fluid progresses through a channel or pipe. In unsteady flow conditions, the hydrodynamic characteristics are not stable, which can be influenced by various factors like flow obstructions, varying inflow or outflow rates, or changes in cross-sectional area.

The distinction between unsteady and steady flow is crucial in fluid dynamics. In steady flow, all parameters remain constant across time, meaning if you measure them at any point in the flow, they would stay the same. Similarly, uniform flow implies that the parameters are not just constant over time but also consistent throughout the entire flow cross-section, which does not align with the characteristics of unsteady flow where variability occurs. Additionally, when depth does not vary, it usually indicates a constant flow condition, further supporting stability rather than the unsteady behavior being assessed.