Structure of 3D turbulent wall jets: acoustic doppler velocity measurements

Abstract

The main aim of this research is to understand and describe key aspects of the structure of turbulent jets and plumes and their interaction with coherent structures together with the effects connected with them (for example boundary layer - jet interactions). The present work is based principally on experiments. We will discuss and compare here the different series of detailed experiments that have been performed in the Laboratory of Fluid Dynamics of the UPC. Measurements of the 3 components of turbulent velocity and their spectra are presented in order to obtain a basic understanding on the interaction that leads to mixing and mass transport in wall jets, where there is coupling between the boundary and the jet or free shear layer structure. We aim to compare different wall and boundary effects on the structure of jets including vorticity production. We present ADV velocity measurements along the centreline of wall jets and compare mean and fluctuating velocity components as well as their PDF’s and spectra. The turbulent interactions between the jet structure and the boundary layer structure generated by the wall are discussed taking into account both the inverse and direct cascades of the jets as a function of their distance to the wall. These complex non homogeneous jets occur in many industrial and environmental applications and elucidating their structure will be useful for better estimates of entrainment, mixing efficiency and other useful parameters. The 3D turbulent wall jet configuration occurs in several applications such as aeronautics design, heating, cooling, ventilation and environmental fluid dynamics