Flow Classification — Time Variation of Discharge A flow in which the quantity of liquid flowing per second changes with time (i.e., not constant in time) is called:

Introduction:
Classifying fluid motion helps engineers choose the right analysis tools. Besides spatial patterns (laminar vs turbulent), we also describe how flow variables change with time at a fixed point—steady versus unsteady.

Given Data / Assumptions:

• Observation at a fixed location in space (Eulerian view).
• Quantity of flow per second (discharge) varies with time.
• Single-phase, incompressible liquid context.

Concept / Approach:
Steady flow means that properties such as velocity, pressure, and discharge at any fixed point do not change with time (∂/∂t = 0). When these quantities vary with time, the flow is unsteady. This definition is independent of whether the flow is laminar or turbulent.

Step-by-Step Solution:
Identify the given condition: discharge is not constant with time.Relate to definition: time variability at a point implies unsteady behavior.Conclude the correct classification: unsteady flow.

Verification / Alternative check:
Examples include pump start-up/shut-down, tidal variations in canals, and hydrograph responses where discharge varies with time—these are classic unsteady scenarios.

Why Other Options Are Wrong:
Steady flow requires time invariance; streamline flow is a dated synonym for laminar and does not address time change; turbulent flow describes disorderly fluctuations in space but can still be steady on average.

Common Pitfalls:
Equating turbulence with unsteadiness; forgetting that a statistically steady turbulent flow can have constant time-averaged discharge.

Final Answer:
unsteady flow