Experimental investigation of a vertical, round, turbulent, momentum jet in a vegetated crossflow

Measurements of the velocity and turbulence characteristics of a vertical, round, turbulent jet discharged into a vegetated crossflow are reported. In recent years up to now a large number of experimental studies and models on turbulent jets discharged into a crossflow have appeared in the literature. As regards these studies, a lack of data concerning the vegetation effects on the jet behavior was observed. The present study was directed toward obtaining a more thorough understanding of the effects of a vegetated bed channel on a momentum (non-buoyant) jet. To achieve this, several experiments were carried out in a rectangular channel at the hydraulic laboratory of the Water Engineering and Chemistry Department of the Technical University of Bari (Italy). To simulate vegetation stems, orderly arrays of rigid circular cylinders, made of steel, were used along an experimental area of 3.00 m long and 0.40 m wide. The jet source was placed at the center of the experimental area. The hydrodynamic features of the jet have been studied with details via turbulence statistical analyses (e.g. velocity field, turbulence intensity and Reynolds stresses). It was found that the background turbulence generated by the vegetation strongly affects the jet behavior, i.e. the jet flow structures become more complex and the jet penetration height, dilution, and spreading increase significantly due to the increase of the turbulence intensities and the shear stresses.