Georges Le Palec

Numerical and experimental study of Boussinesq wall horizontal turbulent jet of fresh water in a static homogeneous environment of salt water

This paper investigates a numerical and experimental study about buoyant wall turbulent jet in a static homogeneous environment. A light fluid of fresh water is injected horizontally and tangentially to a plane wall into homogenous salt water ambient. This later is given with different values of salinity and the initial fractional density is small, so the applicability of the Boussinesq approximation is valid. Since the domain temperature is assumed to be constant, the density of the mixture is a function of the salt concentration only. Mathematical model is based on the finite volume method and reports on an application of standard k-ε turbulence model for steady flow with densimetric Froude numbers of 1–75 and Reynolds numbers of 2 000–6 000. The basic features of the model are the conservation of mass, momentum and concentration. The boundaries of jet body, the radius and cling length are determined. It is found that the jet spreading and behavior depend on the ratio between initial buoyancy flux and momentum, i.e., initial Froude number, and on the influence of wall boundary which corresponds to Coanda effect. Laboratory experiments were conducted with photographic observations of jet trajectories and numerical results are described and compared with the experiments. A good agreement with numerical and experimental results has been achieved.

Investigation of a turbulent wall jet in forced convection issuing into a directed coflow stream

ABSTRACT In the present paper, we have studied numerically the directed coflow stream effects on mean and turbulent flow properties of a turbulent plane wall jet in forced convection emerging into a directed coflow stream. The system of equations governing the studied configuration is solved with a finite difference scheme using a staggered grid for numerical stability, not uniform in the two directions of the flow. The modified version of the first-order low Reynolds number k–ϵ turbulence model is used and compared to existing experimental findings. It is found that predicted results are in satisfactory agreement with the experimental data and that the wall jet fluid decays faster in presence of a directed coflow stream. Results show also that the increase of coflow deviation angles causes an increase of the growth rates of the dynamic and thermal half-width of the jet and enhances the turbulent mixing. It is found that the longitudinal development of normalised forms of the jet characteristics parameters at different directed coflow velocity ratios can be reasonably well collapsed onto universal trends through the use of momentum length scale.

Numerical Study of Wall Horizontal Turbulent Jet of Freshwater in a Homogeneous Co-flow Stream of Saltwater

The disposal of effluents in nature and more particularly in the sea is a very frequent practice. The discharge of wastewater into a receiving environment such as seawater is generally in the form of a turbulent jet. The efficiency of the dispersion of the jet depends on its characteristics of mixing with the ambient environment and when the latter is in motion, it is significantly modified. This paper investigates a numerical study about buoyant wall turbulent jet in co-flow stream. A light fluid of freshwater is injected horizontally and tangentially to a plane wall into homogenous moving environment of saltwater. Since the domain temperature is assumed to be constant, the density of the mixture is a function of the salt concentration only. The mathematical model is based on the finite volume method and reports on an application of standard turbulence model k-e for steady flow with densimetric Froude number of 11 and Reynolds number of 3800. The aim of this work is to predict the influence of the co-flow stream on the dispersion of the jet and the mixing processes between freshwater jet and ambient saltwater. The concentration contours, the cling length, and the central trajectory of the jet are determined. It is found that the jet behavior depends on the co-flow-to-jet velocity ratio.

Turbulent-Heated Plane Compressible Jet Emerging in a Directed Co-Flowing Stream

In this present work, we have studied the directed co-flow effects on mean and turbulent flow properties of a turbulent heated plane jet with variable density discharging into a directed co-flowing stream. The first order k-eturbulence model is applied and has been compared with the existing experimental data. The Finite Volume Method (FVM) is used to discretize governing equations. First of all, it is found that predicted results are in satisfactory agreement with the experimental findings. Moreover, the numerical results of the mean and turbulent quantities has been presented and discussed in this work. The major interest of presenting this model is that to show the importance of the directed co-flow with a positive angle, which is enhancing the mixing. Furthermore, a qualitative analysis of the air entrainment would suggest that the higher inlet hot air jet temperature affect more the lateral in flow of air into the jet and jet lateral expansion is augmented when the inlet hot air jet temperature increases. Therefore, the increase of the inlet hot air jet temperature decreases faster the axial mean velocity and thus more entrainment air is required.