Etude numérique et expérimentale de jets libre ou impactant une plaque plane chauffée

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Numerical study of a turbulent plane jet in a coflow environment

International audienceThe influence of the coflow velocity ratio on the behavior of a turbulent plane jet in forced convection was numerically investigated. A finite difference method was used to solve a system of coupled partial differential equations. A comparison was carried out between the numerical results obtained in the present work and the experimental data reported in the literature. It was found that the investigated model reasonably predicts the mean flow properties of the flow field. The present investigation suggests that the potential core length increases as the velocity ratio rises. Analyses of the mean and turbulent parameters showed that, when using a momentum length scale, parameters can reach an asymptotic curve, at different velocity ratios. (C) 2013 Elsevier Ltd. All rights reserved

Computational study of mixing behaviour of a turbulent jet issuing in a uniform counterflow at low velocity ratios

International audienceThis paper proposes a computational study for the analysis of the velocity and the scalar concentration field of a round turbulent jet flowing into a uniform stream in opposite direction. The investigation is carried out for a range of low jet-to-counterflow velocity ratios; R = 1.3, 1.6, 2.2, 3.1 and 3.4. The Reynolds stress model is applied in numerical simulation to compare obtained results with experimental data from the literature. It is found that predicted results are in good agreement with the experimental data and that the jet fluid decays faster in the presence of a counterflow. The linearity between the penetration distance and the velocity ratio is verified and the axial fluctuating velocities along jet centreline appear to have two distinct peaks, except for the stronger counterflow. The enhanced mixing efficiency of the counterflowing jet is verified through the radial distribution of velocity and scalar concentration at different streamwise stations

Three-dimensional study of turbulent flow characteristics of an offset plane jet with variable density

International audienceAn experimental and numerical investigation of the flow field of variable density turbulent offset jet is presented. The velocity measurements are performed using a Velocimetry Laser Doppler technique for an offset height h. Three cases of variable-density turbulent plane jets discharging from a rectangular nozzle into a quiescent medium are studied. The variation density jets considered were revealed at different Reynolds numbers. In the second step of this work, a numerical three-dimensional model of the problem is simulated through the resolution of the Navier-Stokes equations by means of the finite volume method and the Reynolds stress model second-order turbulent closure model. A non-uniform mesh system tightened close to the emitting nozzle and both the vertical and horizontal walls is also adopted. A good level of agreement was achieved, between the experiments and the calculations. Once the model validated, our model allowed the evaluation of the influence of the variation density on the characterizing features of the resulting flow filed. It is found that the centerline velocity and concentration of the heavier jet decays much faster than in the two other jets, and a similar behavior for the vertical profiles in the three variable-density jets is well reproduced in the simulation

Numerical study of turbulent round jet in a uniform counterflow using a second order Reynolds Stress Model

International audienceA turbulent round jet issuing into a uniform counterflow stream is computationally investigated together with comparison with earlier experiments data, including velocity component along the jet axis and the radial direction. The simulation is carried out using the Reynolds Stress Model (RSM). Numerical results agree well with experimental results and the penetration and spreading of the jet are studied. The turbulence feature of the counterflowing jet indicates that the root-mean-square (rms) of axial velocity fluctuation (root u'(2)) has two distinct peaks whose the second is a specificity of the jet into a counterflow, located within the region near the stagnation point. As the centerline velocity, the centerline temperature is found to decay more rapid when the jet-to-current velocity ratio is smaller. The spreading of the jet is also interpreted by the growth of both momentum width and temperature width of the counterflowing jet leading to that the presence of a counterflow enhances the mixing of the jet. (C) 2015 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved

Computational Study of Velocity Field of a Counterflowing Circular Jet

Sixth Conference on Design and Modeling of Mechanical Systems (CMSM 2015), Hammamet, TUNISIA, MAR 23-25, 2015International audienceThis paper treats the complex and very interesting ``round jet in uniform counterflow stream'' configuration which is known to enhance mixing and dispersion efficiency owing to flow reversal. The complexity of the problem originates from the interaction occurring between the jet and the counterflow. The interest of this configuration is essentially due to its presence in various applications (disposal of wastewater into seas or rivers, premixing fuel in aircraft engines, combustion, etc ...) and in more than a field (industrial, environmental, chemical engineering, etc ...). For the matter, a computational study of a turbulent circular jet discharging into a uniform counterflow is conducted in order to investigate the characteristics of the mean velocity field of the jet fluid. The investigation is carried out for three different cases of jet-to-current velocity ratios; low, median and high velocity ratios. The Reynolds Stress Model (RSM) is used in the comparison with available experimental measurements. The decay of the centerline velocity and the dynamic proprieties of the flow together with radial profiles of axial velocity are computationally analyzed in this paper

Numerical and experimental study of a jet in a crossflow for different velocity ratio

International audienceThis paper deals with a flow generated by the interaction between a circular jet and a crossflow for different velocity ratios (R = v(0)/u(infinity)). This particular side of this study is of extremely high interest as it allows a better understanding of the mixing process of different interacting flows. This work presents experimental results obtained by means of the particle image velocimetry technique to track the evolution of the jet among the environment flow. Results showed the dependence of the emerging jet flow structure on its ratio velocity. A three-dimensional numerical model with a second-order turbulent model (RSM) and a non-uniform grid system is used to examine the behavior of the emerging jet in the crossflow. The comparison of the numerical and experimental results gives satisfactory agreement

Experimental and numerical study of an offset jet with different velocity and offset ratios

International audienceThe present study examines the configuration of an offset jet issuing into either a quiescent medium or a moving stream (co-flowing). The mean velocity and turbulence characteristics of the turbulent offset jet have been investigated using a particle image velocimetry technique at three velocity ratios and for two offset ratios. A numerical simulation of a three-dimensional offset jet has also been carried out by comparing the corresponding results with previous experimental data and our measurements. The numerical investigation was performed by means of the finite volume method together with a second-order turbulent closure model - the Reynolds stress model (RSM) - to examine the behavior of the flow for different velocity ratio and offset ratios. Results give a satisfactory agreement between the experimental data and the calculations. Data from the early flow region clearly show a significant influence of the velocity ratio and the offset ratio on the mean flow and turbulence characteristics

Computational study of mass and heat transport in a counterflowing turbulent round jet

International audienceThis paper investigates the aspect of a hydraulic round jet issuing into a uniform counterflow under a range of jet-to-current velocity ratios. The prediction of the centerline dilution of jet effluent at velocity ratios ranging from 3 to 15 is performed using the Reynolds Stress Model (RSM). The penetration length is determined by considering the 5% contour of the centerline concentration and compared with empirical relationships suggested by previous researches. A similarity analysis is conducted on the radial profiles of both mean concentration and temperature at successive streamwise stations. The heat transport between the jet fluid and the opposed stream is also investigated with emphasis on the temperature effect on characteristics of the concentration field. (C) 2016 Elsevier Ltd. All rights reserved