Experimental Studies on Countermeasure to Reduce Water Surface Fluctuation in the Isawa Main Canal

Abstract

A large fluctuations of water surface is observed in the Isawa Main Canal, Iwate Prefecture. High surface wave due to the intensive vortex in the stilling basin below the drop structure moves downstream. This phenomenon results in a large scale of surface fluctuation. Countermeasure to reduce fluctuation without over all reconstructing the flume are studied by hydraulic model experiments. Surface fluctuation is reduced by floating a buoyant body whose shape is a inverted trapezoid or a flat sheet. The effects of reducing fluctuation by some types of buoyant bodies are clarified by the image analyzing system.
What is the most effective shape of buoyant body or possible problem is examined in a half-size flume compared with the original one. It reduces under half of one at some test case. However, because the test body cannot float by itself, the proper height of fixing a body is studied again by flume experiments.