The hydraulic radius of a fluid conduit is defined as which of the following?

The hydraulic radius is a crucial concept in fluid mechanics, particularly in the analysis of open channel flow and flow in conduits. It is defined as the ratio of the cross-sectional area of the flow to the wetted perimeter of the conduit.

In this context, the cross-sectional area refers to the area that is occupied by the fluid, while the wetted perimeter is the length of the contact surface between the fluid and the walls of the conduit. The hydraulic radius is important because it is used in formulas to calculate flow velocity and discharge and is a key parameter in the analysis of fluid behavior.

The use of the hydraulic radius helps engineers understand how effectively a conduit will convey fluid. A larger hydraulic radius generally indicates more efficient flow since it suggests that a greater area is available for the fluid to travel through, relative to the surface area in contact with the fluid.

In terms of the other options, while they may contain relevant measures (such as mean radius or other ratios), they do not adhere to the standard definition of hydraulic radius, which specifically focuses on the area of flow divided by the wetted perimeter. Therefore, the correct and definitive characterization of hydraulic radius is found in the choice indicating it is the cross-sectional area in flow divided by the wetted perimeter