Correct Answer - Option 4 : Vortex flow
Concept:
Vortex flow:
The motion of a fluid in a curved path is known as vortex flow.
When a cylindrical vessel containing some liquid is rotated about its vertical axis, the vortex flow will be followed by liquid.
Vortex motion is of two types:
1. Forced vortex:
- In the forced vortex, fluid moves on the curve under the influence of external torque.
- Due to the external torque, a forced vortex is a rotational flow.
- As there is the continuous expenditure of energy, Bernoulli's equation is not valid for forced vortex.
- For forced vortex, v = rω is applicable.
- Examples:
- The flow of water through a runner of the turbine.
- Rotation of water in the washing machine.
2. Free vortex:
- When no external torque is required to rotate the fluid mass, that type of flow is called a free vortex.
- As there is no torque in the free vortex, so free vortex is an irrotational flow.
- For free vortex, a moment of momentum is constant i.e. vr = constant.
- Examples:
- The flow of liquid through a hole provided at the bottom of a container.
- Draining the bathtub.
∴vortex flow is both rotational and irrotational flow depending on the torque applied.
