Hervé Bournot

Flow Field Measurement in a Crossflowing Elevated Jet

Structural features resulting from the interaction of a turbulent round jet issuing transversely into a uniform stream are described with the help of flow visualization and the PIV technique. The jet exits from a rigidly mounted pipe projecting at a distance from the floor of a tunnel. The aim of the present work is to investigate the flow structure in the near-field jet-pipe exit. Jet-to-crossflow velocity ratios from 0.375 to 3 were revealed at Reynolds numbers from 1660 to 6330. Flows in the vertical symmetry plane and horizontal plane across the jet-wake, jet-exit, and pipe-wake regions are investigated. The measured velocity fields present quantitative characteristics of the streamlines, vortices, and topological features of the flow structures. In particular, the origin and formation of the vortices in the wake are described and shown to be fundamentally different from the well-known phenomenon of vortex shedding from solid bluff bodies.

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

The 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.

Numerical Simulation of Wave-Structure Interaction around an Obstacle

In this work, we study a turbulent two-phase free surface flow around an obstacle in unsteady regime. A dynamic study relating to the formation of coherent vortex structures enables us to determine the shape of the flow and to clarify its main characteristics (shear layer, recirculation and reattachment). We determine first the dynamic structure of the flow through a numerical approach using the computer code ANSYS Fluent (closure model is k-e). In the second part we study the impact of these vortices on such configurations. A series of numerical simulations have been conducted to further verify the applicability of this model for wave simulations interaction with vortex structures of various shapes.

Numerical Study of a Gas Jet Impinging on a Liquid Surface

The present study introduces a numerical model for one of the most important fluid–fluid interaction problems in industrial engineering applications, mainly a gas jet impinging perpendicularly onto a liquid interface. A better understanding of the process of the interaction of this type of flow was performed using the Reynolds Stress Model (RSM). The Volume Of Fluid (VOF) method is employed to follow the deformation of the liquid surface. The results from the numerical tests are comparable with those presented by Munoz (Appl Math Model 36:2687-2700, 2012) and it is found that computational results agreed well with experimental data. The obtained numerical results provide useful insight and a better understanding of the highly complex flow encountered in such processes. Moreover, we propose to examine the effect of the nature of the liquid on the development of the global flow. Dynamic characters of liquid surface such as the presence of the cavity and the formation of the wave were displayed.

CFD Modeling of Wastewater Discharges in a Sewer System

The malfunctioning of combined sewer systems can lead to an uncontrolled discharge of wastewater into receiving environments causing very serious pollution. The protection of these environments requires a control of the flows and the pollutants concentration. This approach takes into account the hydraulic operation of the sewer systems and the mechanism of the pollutant transfer. In this work, we are interested in a portion of a sewer system of Monastir city in order to reproduce the hydraulic phenomena that occur there. The numerical study was treated using “ANSYS Fluent” software. The standard k-e turbulence model and the multiphase VOF model are used in this work. The exploitation of the results is mainly carried out on the flow rates, the water velocities, and the free surface. Then, we described the evolution of the pollutant concentration, the free surface, and the sediment deposition by examining the various mechanisms of the turbulent flow.

Effect of Froude Number on the Turbulent Wall Jet in Coflow Stream

The influence of the coflow velocity ratio on the behavior of a non isothermal turbulent wall jet has been determined numerically. The numerical resolution of the governing equations is carried out using a finite difference method. Turbulence modeling is performed by a modified low-Reynolds number k–e model. In this work, we are interested in the study of the effect of the coflow stream on the behavior of the dynamic and thermal properties of the wall jet subjected to a constant temperature. A comparison with a simple wall jet is carried out. Further, we will examine the influence of the Froude number on the wall jet emerging in a coflow stream.