Question

When a valve is suddenly closed on a liquid flowing through a long pipe, the pressure wave of high intensity thus generated, is known as:
1. water hammer
2. pressure wave
3. flow hammer
4. jet hammer

Answer 1

Correct Answer - Option 1 : water hammer

Concept:

• When the water flowing in a long pipe is suddenly brought to rest by closing the valve or by any similar cause, there will be a sudden rise in pressure due to the momentum of the moving water being destroyed.
• This causes a wave of high pressure to be transmitted along the pipe which creates noise known as knocking.
• This phenomenon of the sudden rise in pressure in the pipe is known as water hammer or hammer blow.
• A water hammer is developed in a Penstock.
• The magnitude of pressure rise depends upon :
  • The speed at which the valve is closed
  • Velocity of flow
  • Length of pipe
  • Elastic properties of pipe material as well as that of the flowing fluid.