Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Ideal and real fluids, properties of fluids
Question Statement:
If the density of a fluid changes from point to point in a flow region, the flow is called
Options:
(A) steady flow
(B) unsteady flow
(C) non-uniform flow
(D) compressible flow
Official Answer Key:
D
Step-by-Step Solution & Explanation
Flow classifications are defined along different axes: steady/unsteady refers to whether properties change with time at a point; uniform/non-uniform refers to whether velocity changes with position at a given instant; and compressible/incompressible refers specifically to whether fluid density varies within the flow field. Since the question describes density varying from point to point (a spatial density variation — the hallmark property that distinguishes compressible from incompressible flow analysis), the correct classification is compressible flow, option (D). Non-uniform flow (C) is the classic distractor here because it also concerns spatial variation, but it is defined in terms of velocity, not density.
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