In which flow do fluid particles move in parallel or concentric layers with minimal mixing between layers?

In which flow do fluid particles move in parallel or concentric layers with minimal mixing between layers?

• A. Turbulent flow
• B. Laminar flow
• C. Transitional flow
• D. Steady flow

Answer: (B)

Laminar flow. In this regime the fluid moves in smooth, orderly layers that slide past one another mainly under viscous forces, so adjacent layers keep their identities with minimal mixing. The velocity profile across the cross-section is smooth (parabolic in a pipe), and there isn’t the chaotic stirring seen in turbulence. This behavior arises at low Reynolds numbers where viscous effects dominate inertial effects. By contrast, turbulent flow features irregular fluctuations and substantial mixing between layers, while transitional flow sits between these two. Steady flow refers to whether flow properties stay constant in time, not to the presence of layering, and laminar flow can be steady under constant conditions.

Laminar flow. In this regime the fluid moves in smooth, orderly layers that slide past one another mainly under viscous forces, so adjacent layers keep their identities with minimal mixing. The velocity profile across the cross-section is smooth (parabolic in a pipe), and there isn’t the chaotic stirring seen in turbulence. This behavior arises at low Reynolds numbers where viscous effects dominate inertial effects. By contrast, turbulent flow features irregular fluctuations and substantial mixing between layers, while transitional flow sits between these two. Steady flow refers to whether flow properties stay constant in time, not to the presence of layering, and laminar flow can be steady under constant conditions.