Section 4: Soil and Water Conservation Engineering
Specific Energy, Critical Flow & Hydraulic Jump
Subtopic: Specific energy and critical flow
Question Statement:
If subcritical flow approaches a channel width contraction on the specific energy curve without any bed elevation change, which of the following will occur at the contracted section (assuming critical flow is not exceeded)?
Options:
(A) Unit discharge q increases
(B) Water surface depth y decreases
(C) Specific energy E remains constant (neglecting losses)
(D) Froude number Fr increases towards 1.0
Answer Key:
A, B, C, D
Step-by-Step Solution & Explanation
Since $b$ decreases, $q = Q/b$ increases. On the $E-y$ plane with constant $E$, higher $q$ curves lie to the right, causing subcritical depth to drop toward critical depth and $Fr$ to rise toward 1.