Question

“Power required for turbulent flow is independent of the viscosity of the fluid but proportional to fluid density”, this statement is applicable to which type of regime?

(a) Laminar regime

(b) Turbulent regime

(c) Transition regime

(d) Streamline regime

This question was posed to me in an online quiz.

The origin of the question is Power Requirements for Mixing topic in chapter Fluid Flow and Mixing of Bioprocess Engineering

Answer 1

The correct answer is:

(b) Turbulent regime

Explanation:

In the turbulent regime, the flow becomes chaotic, and the power required for mixing is primarily dependent on the fluid density and velocity, but independent of the viscosity. This is because, in turbulent flow, the inertia of the fluid dominates over the viscous forces.

• In turbulent flow, the eddies and swirls cause the fluid to mix vigorously, and the resistance to flow is more influenced by the fluid's density and the speed of movement rather than by its viscosity.

• In contrast, in the laminar regime, the flow is smooth, and viscosity plays a more significant role in dictating the flow resistance, meaning that the power required for mixing is dependent on both the viscosity and fluid density.

The transition regime occurs between laminar and turbulent flow, where both inertial and viscous forces are significant.

The streamline regime refers to laminar flow, where fluid particles move in smooth paths or "streamlines," and viscosity is more important for determining power requirements.

Thus, the statement in the question refers to the turbulent regime.