In the context of fluid mechanics, what defines steady flow?

• A. Flow parameters do not change with time
• B. Flow is turbulent
• C. Velocity changes continuously
• D. Pressure gradient is constant

Answer: (A)

Steady flow in fluid mechanics is characterized by flow parameters—such as velocity, pressure, and density—that remain constant over time at any given point in the fluid. This means that if you were to observe a specific point in the flow, the conditions at that point would not vary as time progresses. When analyzing systems involving fluid flow, assuming steady conditions simplifies the equations of motion and allows for more straightforward predictions of how the fluid will behave.

Other choices provide different conditions that do not represent steady flow. For instance, turbulent flow refers to chaotic changes in pressure and flow velocity, which inherently means that flow parameters are not constant over time. Continuous changes in velocity also do not fit the definition of steady flow, as they imply that conditions at a point are varying. Lastly, while a constant pressure gradient can occur in steady flows, it does not define the term itself, as steady flow can exist even with varying pressure gradients. Therefore, the defining characteristic of steady flow is that flow parameters do not change with time.