Experimental Characterization of straight compound-channel turbulent field

Abstract

Straight compound-channel flows have been studied by many authors, mainly concerned with mean flow variables. Detailed information on the complex turbulent field of these flows is still scarce. In the present paper, high data rate measurements were obtained for the streamwise and vertical velocity components, using a 2D Laser Doppler Velocimeter in a experimental compound flume. The filtered velocities time series allowed the computation of relevant turbulence statistics: autocorrelation functions, dissipation spectra, turbulence scales and dissipation rate. The results are analyzed by comparison with universal laws drawn for isotropic turbulent 2D fully developed open-channel flow. The presence of strong secondary currents does not affect the universal law in the floodplain, as long as the constants are changed. In the main channel the 3D behavior of the flow is more pronounced and the universal laws fail to reproduce accurately the experimental results