Flow Regime – Definition of Non-Uniform Flow A flow in a pipe or channel is called non-uniform when the mean velocity changes from section to section along the direction of flow, even if discharge is steady in time.

Introduction:
Engineers distinguish spatial variation from temporal variation when classifying flows. Recognizing non-uniform flow is key to choosing the right governing equations and approximations for gradually varied or rapidly varied conditions.

Given Data / Assumptions:

• Single-phase liquid in a duct or open channel.
• Focus on spatial variation along the streamline direction.
• Time variation may or may not be present.

Concept / Approach:

Uniform flow means velocity is the same at all cross sections along the flow direction (though it can vary within a section). Non-uniform flow means the sectional mean velocity varies with position. Steady flow concerns variation with time at a fixed location. The two concepts are independent.

Step-by-Step Solution:

Verification / Alternative check:

A gradually varied backwater curve in an open channel is steady in time but non-uniform in space; measured depth and velocity change along the reach.

Why Other Options Are Wrong:

Option A: Describes uniform flow. Option C: Constant discharge defines steady flow, not spatial uniformity. Option D: Definite path is a streamline concept, not a uniformity criterion. Option E: Equal pressure at all sections is rarely true and unrelated to uniformity.

Common Pitfalls:

Equating steady with uniform; ignoring that internal velocity profiles can be non-uniform even when the mean is spatially uniform.

Final Answer:

the liquid particles at different sections have different velocities