What type of flow occurs when fluid properties remain constant with respect to time?

Steady flow is characterized by fluid properties such as velocity, pressure, and density remaining consistent over time at any given point in the fluid. This means that if you were to measure these properties at a specific location within the flowing fluid, they would not change as time progresses. Steady flow is commonly seen in systems where the flow conditions are stable, such as in many engineering applications where flow rate and other parameters are maintained constant.

In contrast, unsteady flow occurs when these properties change with time, meaning that if you were to take measurements at a point during different time intervals, the results would vary. Transitional flow contains elements of both steady and unsteady flow, typically occurring in scenarios where flow conditions are shifting from laminar to turbulent or vice versa. Viscous flow pertains to the effects of viscosity on fluid behavior but does not specifically correlate with changes in steady versus unsteady states.