Study of Energy Dissipation and Downstream Flow Regime of Labyrinth Weirs

In this study, energy dissipation and downstream flow regime of labyrinth weirs are investigated. For comparison of results, equation of maximum possible amount of energy dissipation Delta E-max on labyrinth weirs is obtained by using the specific energy curve. Experimental results supported by dimensional analysis indicated that relative energy dissipation on labyrinth weir Delta E/E-0 is linearly decreased with increasing relative critical depth y(c)/E-0, where E-0 is the total upstream energy. Collision of oblique supercritical flows at the base of nappes created a hydraulic jump on downstream of labyrinth weir. This hydraulic jump stabilized the subcritical flow regime on downstream of weir. Total dissipated energy on labyrinth weir is approximately equal to the maximum possible amount of energy dissipation. Therefore, energy dissipation structures are not required on downstream of the weir. Collision of nappes, circulating flow in created pool behind the nappes, and placing a hydraulic jump on weir downstream face are the main reasons of large energy dissipation on labyrinth weirs.