16th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 09-12 July, 2012 - 1 - Tomographic PIV and Planar Time-resolved PIV Measurements in a Turbulent Slot Jet Artur V. Bilsky 1,2 , Vladimir A. Lozhkin 1 , Dmitry M. Markovich 1,2* , Maxim V. Shestakov 1,2 , Mikhail P. Tokarev 1,2 1: Institute of Thermophysics, Siberian Branch of RAS, 1 Lavrentyev Avenue, Novosibirsk, 630090, Russia 2: Department of Physics, Novosibirsk State University, 2 Pirogova Str., Novosibirsk, 630090, Russia * correspondent author: dmark@itp.nsc.ru Abstract The structure of a quasi-two-dimensional turbulent jet in a narrow channel was investigated experimentally in this work. Study of spatio-temporal flow structure was produced by the Time-resolved PIV technique. The 3D flow structure in the near field of the jet was studied by Tomographic PIV. Secondary flows in the bounded jet were obtained by Tomographic PIV for the first time. 1. Introduction Jet flows are one of the most common forms of fluid dynamics in technological and natural systems. Recently, researchers are paying particular attention to micro and mini jets in a confined space. This is due to general trends in the development of small-scale technical systems. The jet in a narrow or slot channel has a number of features that significantly distinguish it from free jets and flows in channels. The presence of the bounding surfaces leads to different characteristic scales: small-scale three-dimensional flow with a maximum scale of the order of a channel depth and quasi-two-dimensional large-scale flow with the characteristic scales greater than the channel depth (Bilsky et al. 2007). The features of such flows allow investigating the properties of quasi-two- dimensional turbulence and the mechanisms of interaction between large-scale two-dimensional structures and small-scale three-dimensional turbulence in a laboratory. Heskestad (1965) showed that the jets in confined channels cannot be described by two-dimensional flow equations. Secondary flows are formed near the bounding planes inside a jet shear layer which lead to a significant three-dimensional flow. Features of the bounded two-dimensional jets have been studied in Foss and Jones (1968). The authors showed that the flat bounded jet is not a superposition of two flows: a boundary layer and a two-dimensional jet. Based on measured velocity distributions in a cross section, the authors proposed a physical model of secondary flows. Later, in the paper Holdeman and Foss (1975) the authors confirmed this effect by the results of hot-wire measurements and direct vorticity strength measurements by a small mechanical turbine. The model assumed that the secondary flows arise from the curvature of the vortex tube, which is formed on an edge of a nozzle. The vortex tube is similar to that formed at the end of the free rectangular jets, but the presence of bounding surfaces leads to the generation of longitudinal vorticity due to bending of the vortex tube near the bounding surfaces. The reorientation of the vortex tube is directly related to its curvature, arising due to the presence of slip at the wall and the velocity gradient near the wall. The authors showed that the secondary flows are completely determined by the longitudinal vorticity. A model based on the curvature of the vortex tube, also confirmed by other authors on the study of three-dimensional wall jet. However, Owczarek and Rockwell (1972) suggest another mechanism of secondary flows in a slot jet. Their model is based on the fact that the sources of secondary flows in the jet flow are rising out of the corners of a rectangular nozzle. The mechanism of secondary flows in rectangular channels, and in semi-infinite angles is well studied and confirmed in many experimental works.