Question

In a pipe flow, the hydraulic grade line will be obtained by the summation of

• A. Pressure head and datum head
• B. Velocity head and datum head
• C. Pressure head and velocity head
• D. Pressure head, velocity head and datum head

Hint:

A simple way to remember the energy lines:
- HGL = Piezometric Head ($z + P/\gamma$)
- EGL = Total Head (HGL + Velocity Head)
The vertical distance between the EGL and HGL is always the velocity head, $v^2/2g$.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
What defines the Hydraulic Grade Line (HGL)?

Step 2: Key Definition (Alternate):
HGL = z + P/γ (datum head + pressure head). EGL = HGL + v²/2g (adds velocity head).

Step 3: Detailed Explanation:
HGL is the level water rises in piezometers along the pipe. EGL is always above HGL by velocity head. In open channels, HGL coincides with water surface.

Step 4: Final Answer:
Sum of pressure head and datum head.