Investigation of the mixing process in an axisymmetric turbulent jet using PIV and LIF
In the present paper, mixing of a passive scalar in a self-preserving axisymmetric turbulent jet at a Reynolds number of 2x103 is studied utilizing combined particle image velocimetry (PIV) and planar laser induced fluorescence (LIF). Detailed measurement
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*1 Gifu University,
Yanagida 1-1, Gifu 501-1193, Japan
*2 Waterloopkundig Laboratorium, Delft Hydrolics, Rotterdamseweg 195, P.O. box 177, 2600 MH Delft, The Netherlands *3 Laboratory for Aero- and Hydrodynamics,
Delft University of Technology,
Leeghwaterstraat 21, 2628 CB Delft, The Netherlands Abstract. In the present paper, mixing of a passive scalar in a self-preserving axisymmetric turbulent jet at a Reynolds number of 2xl0 3 is studied utilizing combined particle image velocimetry (PlY) and planar laser induced fluorescence (LIF). Detailed measurements are made for the mean velocity, turbulent intensity of velocity fluctuation, Reynolds shear stress, mean concentration, concentration fluctuation intensity, and turbulent flux at the center plane of the jet. In order to examine the reliability of the results, mass balances that are based on the mass-balance equation are also estimated. These results will be a reference data set for further investigation of the chemically reacting turbulent jet. The results are compared with the results from direct numerical simulation, point velocity measurements, and combined PlY, particle tracking velocimetry (PTY), or laser Doppler velocimetry (LDY) and LIF measurements. All the properties collapse onto self-similar profiles in the far field (30-60 diameter downstream from the nozzle) of the jet, and agree with the previous data. In the case of the present data, the mass balances are conserved quite well.
Keywords: Combined P1V and LIF, Mixing process, Turbulence, Axisymmetric Free Jet, Turbulent Flux of Passive Scalar, Mass-balance
1. Introduction Turbulent jet flow has been widely studied for its mixing properties. Mixing of passive scalars, such as heat or contaminants, is one of the significant features of the turbulence, and the jet flow in combination with turbulent mixing and the chemical reaction can be found in many practical applications (e.g. fuel injectors
R. J. Adrian et al., Laser Techniques for Fluid Mechanics © Springer-Verlag Berlin Heidelberg 2002
340 in combustion engines). In order to improve the efficiency of such devices, it is important to obtain more insight into turbulent mixing. In the experimental investigation of turbulent mixing, it is necessary to measure the instantaneous velocity and concentration field, simultaneously, since the mixing process can be described as the interaction between a velocity and concentration field. In the present study, we investigated the mixing of a passive scalar contaminant in a turbulent free jet with a surrounding fluid. The Reynolds averaged equation for the conservation of the mean concentration of a passive scalar in an axisymmetric jet is given by,
where U, V and C are the mean axial and radial velocity and the mean concentration respectively, z and rare the axial and radial coordinate respectively, Dis the molecular diffusion coefficient, and uc and ~ are the correlation of the axial and radial velocity fluctuation and the concentration fluctuations respectively. The terms on the left hand side of
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