Characteristics and analysis of a turbulent offset jet including the effect of density and offset height

International audienceThis paper presents the results of measurements and numerical predictions of 3D turbulent offset jet flows. Mean velocity and turbulence characteristics of a rectangular offset jet with different offset heights and within variable densities are experimentally and numerically investigated in detail. Four jet gas exit densities, ρj = 1.2, 1.25, 1.3 and 1.4 Kg/m3, and four offset ratios, h/w = 8, 16, 25 and 33, are studied. The considered variation of the jet density is revealed at different Reynolds numbers and the velocity measurements are carried out using a Laser Doppler Velocimetry (LDV) technique. The handled configuration is numerically simulated by solving the Navier-Stokes equations with the finite volume method having a non-uniform grid system. Two different closure models are tested: the standard k–ε model and the Reynolds Stress Model (RSM). Results clearly revealed significant effects of the jet density and the offset height on the flow development in the early region. It is noted that the centerline velocity decay increases as the jet density and the offset height increase. It is also observed that the reattachment length of the jet decreases with the increase of the jet density. However, the reattachment length is found to increase with the increase of the offset height

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

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

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

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

Experimental and CFD analyses of pollutant dispersion around an isolated cylindrical building

International audienceAn investigation of the dispersion of pollutants ejected from a chim- ney around a three-dimensional cylindrical obstacle within a cross- flow air stream was conducted in this paper. The dynamic evolution of air seeded with glycerin particles ejected from an elevated jet around the isolated obstacle in a wind tunnel was experimentally studied using the particle image velocimetry technique and under different velocity ratios between the chimney ejection and the wind source. The dispersion of CO2 pollutant around the cylindrical build- ing was numerically predicted based on measured experimental data using the finite volume method and the Reynolds stress model. A good agreement between experimental and computational results was found. Velocity, temperature, and concentration results revealed that the velocity of the wind together with the presence of the isolated building obstacle influenced the flow structure

A review on thermal energy storage using phase change materials in passive building applications

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