What is the name of the flow where velocity exceeds a critical speed and the fluid loses ordered layering?

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

Answer: (C)

Flow regimes change from smooth, layered motion to chaotic, mixed motion when inertial forces exceed viscous damping as velocity increases. In laminar flow, fluid layers glide past one another with little cross-mixing, giving a stable and predictable velocity profile. When speed passes a critical threshold, disturbances grow and break the orderly layers into eddies and vortices of many sizes, leading to random fluctuations in velocity and pressure—this is turbulent flow. The term turbulence best describes the state where the flow loses its ordered layering. Poiseuille flow is a classic model of steady laminar pipe flow, not this chaotic condition. Steady flow refers to time-invariant conditions and does not itself imply turbulence; laminar flow is smooth and ordered, opposite of turbulent. So the best answer is turbulent flow.