Field Measurements on the 3D Turbulent Large-scale Structures in the Flood Flow by Multi-channels Simultaneously Measuring System

Abstract

Field measurements on turbulent large-scale structure of a flood flow in the Hinuma river were conducted with 16-channels electromagnetic anemometers. The turbulent velocity components (u, v) at 8 points on a plane perpendicular to the mean flow have been sampled and recorded simultaneously by a A/D converter. The quasi-instantaneous 3D images of coherent structures in the flood flow were reconstructed from these obtained data by using conditional technique and a new method of data analysis. These structures detected near the river bed are low-velocity lumps of fluid and generate intermittently peaks of the high positive Reynolds stress. The high generation of the suspend load in the flood flow may be explained by these structures. Near water surface, coherent structures have also been found and they generated small-scale boils.