Coanda Effect refers to which phenomenon?

• A. Bernoulli Effect
• B. Coanda Effect
• C. Venturi Effect
• D. Turbulent Flow

Answer: (B)

The Coanda effect is the tendency of a moving fluid to attach to and follow the contour of a nearby curved surface. When a jet of fluid issues near a surface, viscosity causes the surrounding fluid to be entrained with the jet. This entrainment lowers the pressure in the gap between the jet and the surface, pulling the jet toward the surface and causing it to hug and follow the surface as it flows. This attachment and curving of the jet along the surface is what the Coanda effect describes.

It’s not simply about changes in pressure from speed (like Bernoulli), nor about pressure drops from constrictions (Venturi effect), and it isn’t about a chaotic flow regime (turbulent flow). The key idea is the viscous attraction and the resulting boundary-layer dynamics that make the jet cling to and ride along the surface.