Abstract
A turbulent velocity field was measured in a vegetated compound open channel flow where vegetation density changed abruptly from low to high and high to low in the downstream direction. The changing process of mean velocity, secondary currents and Reynolds stress fields were explained with three dimensional mixing structure caused by large horizontal eddies. As a result, three dimensional structure of turbulent flow, and relation between mean velocity field and turbulent structure were clarified experimentally in an open channel flow with abrupt change in the vegetation density in the downstream direction.
