Laboratory study of the turbulent structure of a channel jet flowing into an open basin

Abstract

The turbulent structure of a river jet flowing into a lake was simulated in the laboratory. The main purpose of the study was to look for the turbulent coherent structures at a river mouth up to the point where the river defined turbulence ceases to exist. Experiments were conducted at the Caucasia Regional Hydrometeorological Institute at Baku, and final analysis of the data was performed at the Kinneret Limnological Laboratory in Israel. To model the river outgoing jet properly, a sand bottom was applied, which formed the ripples and the bar as in natural conditions. Several days after the beginning of the laboratory experiment, when the bar and the ripples had reached a quasi steady state, the turbulent jet measurements began. Experimental data were gathered by simultaneous recording of longitudinal velocities at different distances between the channel outlet and the sand bar. The records were processed and related turbulent characteristics of the jet flow were obtained. Values of mean velocities, water depths along the jet axis, spectrum of joint velocities at chosen frequencies, and maximal and average size of the coherent structures, were calculated. The patterns of the above parameters enable the description of the decay process of a free turbulent jet flowing out a chanel.