This work concerns the numerical prediction of pesticide deposits on vine by air assisted sprayers. This numerical model consists in two different parts: the air flow characteristics were obtained through a Navier-Stokes solver in which additional terms have been introduced in order to account for the modification of the flow by the vine foliage. The theoretical form of these terms was derived through an averaging procedure. As a result, the canopy effect was modelled by introducing momentum and turbulence source terms in the Navier-Stokes equations. The constants were identified thanks to experimental data obtained by direct measurements of the air flow speeds through an artificial canopy. The second part of the model consists in simulating the droplet cloud by means of a lagrangian stochastic model. The average motion of the droplets was computed through the use of lagrangian coordinates and the turbulence effect on the droplets was interpreted in term of statistical properties of the droplet cloud. The tractor displacements were accounted for through unsteady boundary conditions. Once the size and the droplets cloud locations have been determined, the deposit was predicted for a vine row of one meter length using an efficiency coefficient obtained from simulations. Thanks to this approach we were able to quantify the effect of air turbulence on droplet deposition / Ce travail concerne la prédiction numérique de dépôts dans la vigne de pesticides pulvérisés avec assistance d'air. Le modèle numérique comprend deux parties : les caractétistiques du flux d'air sont obtenues à partir de la résolution des équations de Navier-Stokes dans lesquelles des termes additionnels ont été introduits pour prendre en compte les modifications du flux dues au feuillage. L'effet de la végétation est modélisé en introduisant des termes source de quantité de mouvement et de turbulence dans les équations de Navier Stokes. Les constantes ont été identifiées grâce à des données expérimentales obtenues par des mesures directes des vitesses d'air dans une végétation artificielle. la deuxième partie du modèle représente le nuage de goutteletters à l'aide d'une représentation Lagrangienne stochastique. Le mouvement moyen des gouttes est calculé à partir de leurs coordonnées Lagrangiennes et l'effet de la turbulence est pris en compte dans les propriétés statistiques du nuage; Les déplacements du tracteur sont pris en compte par des conditions aux limites transitoires. Une fois que la taille et la position du nuage de gouttelettes est déterminé, le dépot est calculé sur un mètre de rang de vigne en utilisant un coefficient d'efficacité calculé à l'aide de simulations. Grâce à cette approche, on peut prédire les effets de la turbulence sur le dépôt des goutte

Experimental and numerical investigations have been carried out to study the behaviour of a centrifugal pump operating in direct mode or turbine mode. First of all, the complete characteristics (head, power, and efficiency) were measured experimentally using a specific test loop. The numerical data obtained from a CFD study performed with the ANSYS CFX software and based on steady state and unsteady approaches were compared to the experimental results. The representation in the 4 operating quadrants shows the various operating zones where the head is always positive. Then, the unsteady radial forces were analysed from transient computations. The results obtained for the pump operation are consistent with the literature and extended to the nonnormal operating conditions, namely, for very high flowrate values. The evolution of the radial load during turbine operation is presented for various partial flow operating points.

In some industrial processes, and especially in agrofood industries, the cleaning in place mechanism used for hydraulic circuits plays an important role. This process needs a good knowledge of the hydrodynamic flows to determinate the appropriate parameters that assure a good cleaning of these circuits without disassembling them. Generally, different arrangements are present in these hydraulic circuits, such as expansions, diffusers, and elbows. The flow crossing these singularities strongly affects the process of cleaning in place. This work is then a contribution to complete recent studies of “aliments quality security” project to ameliorate the quality of the cleaning in place. It presents experimental and numerical investigations of a confined turbulent flow behavior across a conical diffuser (2α=16 deg). The role of a perturbation caused by the presence of an elbow in the test section, upstream of the progressive enlargement, was studied. The main measurements were the static pressure and the instantaneous velocity fields using the particle image velocimetry (PIV). Post-processing of these PIV measurements were adopted using the Γ2 criterion for the vortices detection and the proper orthogonal decomposition (POD) technique to extract the most energetic modes contained in the turbulent flow and to the turbulent flow filtering. A database has been also constituted and was used to test the validity of the most models of turbulence, and in particular, a variant of the shear stress transport (SST) model.

The hydraulic performances of the centrifugal pumps are well-known as long as considering normal pump operating conditions but the abnormal operating conditions as energy dissipators or as turbines are less studied. The complete pump characteristics can be reported on a single four-quadrant representation and can be used to predict the behaviour of the machine during the transient operations or to explain the accidental scenarios. This study which is supported by the French manufacturers aims to explore the four quadrant operating conditions of a testing centrifugal pump using experimental and numerical approaches. In the one hand, the experimental test rig afford to perform a series of constant-speed runs varying from negative to positive values in the normal or reverse direction. The range of flowrates is included between −200 to +300 per cent and differs following the rotational speeds. Head, efficiency and torque are measured for all cases, negative or positive discharges. On the other hand, numerical modelling of the same centrifugal pump is performed. CFD computations for a large range of flow rates are analysed. According to the operating conditions, steady state or transient rotor-stator approaches are used to obtain realistic predictions and a discussion concerning the domain of validity of steady state modelling is proposed. Finally, the pump behaviour in the four quadrants obtained by the transient numerical simulations based on two equation turbulence models are in good agreement with the experimental results.

An experimental study is performed in order to describe the single-and twophase (air-water) horizontal flow in the presence of pipe expansion and contraction. Three types of singularities are investigated; smooth convergence and sudden and progressive enlargement. The opening angles for progressive singularities are 5, 8, 9 and 15 degrees. The surface area ratios tested are σ = 0.43, 0.64, 0.65 and 1.56. Bubbly flow is the dominant flow regime that is investigated for volumetric quality up to 30%. The pressure distribution for both single and two-phase horizontal flow is examined versus axial position. For expansion geometries, it is found that the smaller the enlargement angle, the larger the recovery pressure for the same flow conditions; the pressure drop caused by the singularity is higher in the case of a sharper expansion. The comparison of the experimental results to published models leads to a proposed corrective coefficient for Jannsen's correlation. Flow visualization is also performed; the flow patterns downstream from the different singularities are identified in each configuration and plotted in Baker's map for horizontal flow.