Turbulent flow is best described as which?

• A. A smooth laminar flow
• B. A stagnant flow
• C. An irregular pattern of flow with random variations in pressure
• D. A compressible flow

Answer: (C)

Turbulent flow is chaotic and characterized by irregular, swirling motions called eddies that come in many sizes. These eddies cause rapid, random fluctuations in velocity and pressure throughout the flow, so the pattern is not smooth or predictable. This randomness in time and space is what sets turbulence apart from orderly, layered flow. The other descriptions miss this key feature: a smooth laminar flow is orderly and layered; a stagnant flow has no motion; and compressibility deals with density changes, which isn’t what defines turbulence (and turbulence can occur in incompressible fluids too). So the description that best fits turbulent flow is an irregular pattern with random variations in pressure.