Question

In turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube:
A) is zero.
B) is maximum.
C) is equal to critical velocity.
D) may have any value.

Answer 1

Hint: Turbulence flow is not a streamline flow. So, it may have many values of velocity (velocity of liquid) throughout the flow in the tube. The velocity gradients are different at different points of the tube for a turbulent flow.

Complete step by step solution:
Turbulence is generated either by frictional forces or by mass forces.
In the near wall of the tube, turbulence is generated in the region of near wall velocity gradients throughout the flow. The velocity gradients are different at different points of the tube for a turbulent flow. The pressure near the walls of the tube are highest throughout the flow.
Hence, in turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube may have any value.

Therefore, option (D) is correct.

Additional Information:
There are two types of flows.
Streamline flow- It is a type of flow in which the flow undergoes regularly. It doesn’t have any disruptions or intermixing of the layers of the liquid.
Turbulent flow- It is a type of flow in which the flow undergoes irregular fluctuations. It has
disruptions and intermixing of the layers of the liquid.

Note: Turbulent flow has an irregular pattern of liquid flow while streamline flow has a regular pattern of liquid flow. The velocity gradient is constant in streamline flow. The velocity gradient is variable in the turbulent flow.