ANALYSIS OF UNDULAR FREE-SURFACE TRANSITIONAL FLOWS

Abstract

Project engineering in water resources management specifically involves free surface flows in open channels systems. Typical channel control design includes the project of gates and weirs for both discharge measurement and water level control. Current design practice for real projects, however, rely on the use of commercial codes based on the gradually-varied flow theory, as, for example, HEC-RAS. However, this modeling approach is not accurate in many real cases. Under some circumstances the flow conditions deviate from the graduallyvaried flow theory, and the real operational conditions results in dangerous undular free surface flows changing from subcritical to supercritical flow, and vice-versa. These flows are highly different from the assumed standard open channel hydraulics in commercial general codes. In this study an advanced hydraulic modeling approach is proposed for the analysis of undular free surface flow past gates and weirs. The model is successfully verified with experimental data. The solution is detailed, permitting its adoption for design purposes in water resources project engineering practice. Keywords: Frictional effects; hydraulic jump; transitional flow; turbulence; undular flow