27. Undular Jump
A hydraulic jump or other transcritical flow condition may reduce the accuracy of a flow monitor. However, this effect is not strictly limited to critical flow (Fr = 1), but may also occur within a wider range of near-critical flow conditions. Research by Chanson, Hager, and others suggests a range of conditions (0.7 < Fr < 1.7) where unstable flow may exist. Pipe shape and material also appear to affect where unstable flow may occur. This scattergraph is believed to result from an undular hydraulic jump and is characterized by a stair step pattern.