An experimental study on tip velocity and downstream recirculation zone of single groynes of permeability change

Abstract

Groynes usually are installed along the river side and those are used for various purposes including flow and erosion control and bank protection. Recently, the concern of groynes that provide us with ecological environment and improvement of scenary near river has greatly increased for naturalized river and ecological river restoration. However there is no adequate design guideline in Korea. Furthermore there is little research for the installation of groynes in Korea. Especially, since the influence factors of groyne are complexly related to the stream characteristics, hydrologic variables, hydraulic characteristics, and local variables, the analysis considered the influences of all factors is difficult. For that reason, most of existing researches have been focused about local scour at the tip of groynes with sandy bed condition and flow pattern near groynes and recirculation zone. In this study, to evaluate influence factor of the interval of groynes, experiments of flow pattern near groynes and recirculation zone with the variation of permeability, approaching velocity, groyne length, and installed angle have been performed. We also measured the tip velocity of groynes and that is scour factor near groyne. Empirical equations for recirculation zone and tip velocity of gryones were determined.