Characteristics of Water Surface Profile and Velocity Distribution near Series of Piles in Open Channel Flow

Abstract

For improvement of river environment, it is important to make clear flow structures around pilelike construction, for example, bridge piers, series of piles, etc. Former hydraulic studies on cylindrical piers paid much attention to scouring process, mechanism and its prediction for the purpose of bridges' safety. As a result, most of these studies above have not brought up the characteristics of water surface profile and mean flow around them. In this paper, plain characteristics of water surface profile around series of piles are studied on the basis of mean velocitydistribution in open channels.
The results obtained in this study are divided into 3 steps as follows;
1. Water surface profiles and velocity distributions around a single pile and three piles (set closely along a line with attack angle against flow) were measured in the flume tests with fixed bed. Water surface profiles around them were characterized by standing waves and interference between them, and had a close relation with velocity distributions (Calculation-I, Chapter II).
2. The two-dimensional modeling of flow around piles was carried out, based on the analysis of experimental results. The computed results were well confirmed by experimental ones (ChapterIII).
3. Transformation of water surface profiles and velocity distributions around two close piles according to the variation of attack angle were calculated by the two-dimensional model (Calculation II). It was suggested that there was a critical attack angle which corresponds to sudden rise phenomenon of scouring magnitude observed in the former experiments on two close piers(Chapter IV).