Flow net fundamentals in seepage analysis: Identify the correct statement regarding the geometry and properties of flow lines and equipotential lines in a flow net for homogeneous soil.

Introduction / Context:
Flow nets provide a graphical solution to two-dimensional steady seepage governed by Laplace’s equation. Correct interpretation of their geometry underpins estimates of seepage quantity and uplift pressures below hydraulic structures such as weirs and cutoffs.

Given Data / Assumptions:

• Homogeneous, isotropic soil.
• Steady-state two-dimensional flow.
• Properly constructed flow net with flow lines and equipotential lines.

Concept / Approach:

By definition, flow lines represent streamlines and equipotential lines represent loci of equal total head. Laplace’s equation requires these two families of orthogonal curves. The net is ideally composed of approximately curvilinear squares, not rectangles with prescribed 2:1 ratios. Smaller field dimensions do not reduce hydraulic gradient; rather, for a given potential drop per square, shorter path lengths imply larger local gradients.

Step-by-Step Solution:

Verification / Alternative check:

Classic texts show flow nets with nearly square curvilinear fields; orthogonality is a direct consequence of harmonic functions for head.

Why Other Options Are Wrong:

(b) Imposes an arbitrary 2:1 geometry; (c) reverses the gradient behavior; (d) lines are smooth, not “generally circular.” (e) is close to a correct description but does not directly answer the stated property as clearly as (a).

Common Pitfalls:

Ignoring isotropy; poor net drawing that violates orthogonality and square field requirement.

Final Answer:

Flow lines and equipotential lines intersect each other at right angles