Montana flume

The Montana Flume is a restriction with free-spilling discharge that accelerates flow from a sub-critical state (Fr~0.5) to a supercritical one (Fr>1).

The free-flow discharge can be summarized as Where Montana flume discharge table for free flow conditions:[8] Free-Flow – when there is no “back water” to restrict flow through a flume.

A free flow also induces a hydraulic jump downstream of the flume.

In natural stream applications, submerged flow is frequently the result of vegetative growth on the downstream channel banks, sedimentation, or subsidence of the flume.

In practice, is it usual to see Montana flumes larger than 48-inches as the need for free-spilling discharge can not usually be met, downstream scour would be excessive, or other flume types better handle the flow.