Question

Hydraulic gradient is defined as

• A. Change in pressure head length
• B. Change in velocity head length
• C. Change in static head length
• D. Head loss due to friction length

Hint:

Hydraulic gradient $i = \frac{h_f}{L} = \frac{\text{Frictional Head Loss}}{\text{Length}}$. Dimensionless.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The Hydraulic Gradient Line (HGL) represents the slope of the piezometric head along the flow path in closed pipe conduits and porous media.
Key Formula or Approach:
\[ i = \frac{h_f}{L} = -\frac{dh}{dL} \]
where \(h_f\) is frictional head loss and \(L\) is length of conduit.

Step 2: Detailed Explanation:
In fluid mechanics and Darcy's law for flow through porous media/pipes:
The hydraulic gradient \(i\) is defined as the total loss of piezometric hydraulic head (head loss due to friction and viscous drag) per unit length of the flow path:
\[ i = \frac{h_f}{L} \]
It is a dimensionless ratio driving fluid flow against shear resistance.

Step 3: Final Answer:
Therefore, hydraulic gradient is Head loss due to friction length, corresponding to option (D).