If the Froude number is greater than 1, what type of flow is present?

• A. Turbulent flow
• B. Supercritical flow
• C. Subcritical flow
• D. Critical flow

Answer: (B)

When the Froude number is greater than 1, it indicates the presence of supercritical flow. The Froude number is a dimensionless value used to characterize flow conditions in open channel hydraulics and is defined as the ratio of the inertial forces to gravitational forces. Specifically, it is calculated using the flow velocity and the square root of the product of gravitational acceleration and hydraulic depth.

In supercritical flow, the velocity of the fluid is greater than the wave speed, leading to a situation where disturbances travel upstream rather than downstream. This flow condition is typically characterized by shallow, fast-moving water, which can create a variety of hydraulic phenomena and behavior in rivers, over weirs, and in channels.

Understanding supercritical flow is crucial for various engineering applications, as it influences sediment transport, flow behavior over structures, and the design of hydraulic systems.