Existence theory for a kinetic-fluid coupling when small droplets are treated as part of the fluid

We consider in this paper a spray constituted of an incompressible viscous gas and of small droplets which can breakup. This spray is modeled by the coupling (through a drag force term) of the incom- pressible Navier-Stokes equation and of the Vlasov-Boltzmann equation, together with a fragmentation kernel. We first show at the formal level that if the droplets are very small after the breakup, then the solutions of this system converge towards the solution of a simplified system in which the small droplets produced by the breakup are treated as part of the fluid. Then, existence of global weak solutions for this last system is shown to hold, thanks to the use of the DiPerna-Lions theory for singular transport equations

Intensification of phosphate fertilizers granulator using CFD: transition phenomenon investigation FuturE work & perspectives

International audienc

Développement d'un simulateur de terres agricoles et de politiques pour promouvoir des politiques climato-intelligentes

International audienceFeeding 1.5 billion people by 2030, and 2 billion by 2050, while mitigating and adapting to climate change, is a daunting challenge that countries in Africa are attempting to address. In this paper we report in a project between Mohammed VI Polytechnic University (UM6P) and Climate Interactive (CI). Our tool, the Agriculture and Land Policy Simulator (ALPS) helps policy-makers and stakeholders make climate-smart decisions in their agriculture strategies. ALPS models the intersections among land, agriculture, and climate. We base our work on the Climate Smart Agriculture (CSA) concept, the three pillars of which are: food security, resilience to climate changes, and mitigation of emissions. Using System Dynamics, a multidisciplinary team of agronomists, agricultural economists, and system dynamics developed the causal relationships. We refined system structure and formulations based on discussion with experts, existing research, and analysis of strategic policy documents. The model parameters are set to fit historical data from a variety of sources. In this paper we present the Moroccan case of ALPS, incorporating significant improvements over prior work and fitted to the Morocco policy context. The Green Morocco Plan (known by the French acronym PMV) is specifically used for simulation and modeling exercise. The simulator allows the user to test assumptions and scenarios through varying levels on different policy components. ALPS has previously been used to simulate the Ethiopian context, and future development will improve both these cases and will be extended to cover several African countries. The causal loop below summarizes all interactions between the model variables that interlink agriculture sectors. Food Demand increases with population and living standards. The user makes choices to ensure Food Available-Production and Imports less Losses and Exports-can meet demand. Land use can change between five categories-Cropland, Pasture, Forest, Grassland, and Dessert. The availability and need for irrigation depends on rainfall and infrastructure. These physical limits enforce the constraints the agriculture system faces. Action to meet food demand also create undesirable consequences. Countries have goals such as reducing greenhouse gas emissions and deforestation. ALPS includes direct emissions from crop and livestock farming, as well as emissions from land-use changes and the stocks of carbon sequestered in soil and biomass. These help the user see the impact on other goals when meeting food needs

Attitude tracking of a tri-rotor uav based on robust sliding mode with time delay estimation

The paper presents a robust sliding mode with time delay estimation method for controlling the attitude of a tri-rotor unmanned aerial vehicle (UAV) in presence of uncertainties and disturbances. The proposed control algorithm allows high accuracy tracking since a good disturbance estimation is provided using time delay estimation method and allows chattering reduction. The stability analysis of the closedloop system is presented using the theory of Lyapunov. Finally, two numerical simulations are presented in the presence of disturbances to show the effectiveness of the proposed nonlinear control scheme.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Speed control of a five-phase induction motor drive using modified super-twisting algorithm

The present work proposes an alternative for the inner current control based on the modified super-twisting algorithm with time delay estimation. Simulation results were carried out to verify the performance of the proposed robust control strategy for a five-phase induction motor drive. A stability analysis is also presented.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Invagination intestinale sur sonde de jéjunostomie: à propos d’un cas

L'invagination intestinale sur sonde de jéjunostomie est une complication très rare.Nous rapportons le cas d'un patient âgé de 28 ans ayant ingéré l'esprit de sel dans le cadre d'une tentative de suicide. Une fibroscopie 'sogastroduodénale a montré des lésions oesophagiennes et gastriques stade IIb selon la classification de Zargar. Quinzejours après le patient présentait une aphagie pour laquelle il bénéficiait d'une jéjunostomie d'alimentation. L'évolution était marquée par l'installation d'une invagination sur sonde de jéjunostomie ayant nécessité une intervention chirurgicale avec des suites simples. L'amélioration de la prise en charge et du pronostic de l'IIA secondaire à une cause inhabituelle nécessitant un diagnostic précoce. La réduction de cette forme particulière d'invagination est exclusivement chirurgicale.Pan African Medical Journal 2015; 2

Robust finite-time position and attitude tracking of a quadrotor UAV using super-twisting control algorithm with linear correction terms

This work investigates the problem of finite-time position and attitude trajectory of quadrotor unmanned aerial vehicle systems based on a modified second order sliding mode algorithm. The selected algorithm is a modified super-twisting with both nonlinear and linear correction terms.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Finite-time altitude and attitude tracking of a tri-rotor UAV using modified super-twisting second order sliding mode

This paper presents the problem of robust altitude and attitude trajectory tracking of a tri-rotor Unmanned Aerial Vehicle (UAV) based on a finite-time second order sliding mode control algorithm. The chosen algorithm is a modified super-twisting control with double closed-loop feedback regulation that provides fast finite-time convergence even when the system trajectories are far from the sliding surface, robustness against a wide class of uncertainties and disturbances.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Discrete-Time sliding mode with time delay estimation of a six-phase induction motor drive

This paper investigates the problem of stator current control in presence of uncertainties and unmeasurable rotor current for a six-phase induction motor drive. An inner control loop based on a robust discrete-time sliding mode with time delay estimation method is proposed to ensure the finite-time convergence of the stator currents to their desired references while the proportional-integral controller is used for the outer speed control. Sufficient conditions are established to ensure the stability of the closed-loop system. Simulation results were carried out to verify the performance of the proposed robust control strategy for a six-phase induction motor drive.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Multi-fluid flows : mathematical analysis, modelling and simulation

La présente thèse comporte trois parties indépendantes.La première partie présente une preuve d'existence de solutions faibles globales pour un modèle de sprays de type Vlasov-Navier-Stokes-incompressible avec densité variable. Ce modèle est obtenu par une limite formelle à partir d'un modèle Vlasov-Navier-Stokes-incompressible avec fragmentation, où seules deux valeurs de rayons de particules sont considérées : un rayon r1 pour les particules avant fragmentation, et un rayon r2<<r1 pour les particules obtenues par fragmentation. Le modèle asymptotique est obtenu dans la limite r2 tendant vers zéro. La démonstration s'appuie sur des techniques de régularisation et de troncature en vitesse, sur le théorème de Schauder et enfin sur une méthode de compacité de Lions-Di-Perna pour l'élimination des régularisations introduites dans le système initial.La deuxième partie concerne la modélisation de l'impact d'une vague de liquide sur une paroi. L'objectif de cette partie est d'obtenir un modèle pour la fuite du gaz environnant sur les "côtés" de la vague. Un modèle numérique est réalisé en remplaçant la vague liquide par une masse solide indéformable et un schéma VFFC-ALE est conçu pour la simulation numérique du modèle. La mise sans dimension des équations permet de montrer les nombres sans dimension qui régissent le phénomène de fuite. La vitesse moyenne de fuite est comparée à la vitesse dans le cas d'un fluide incompressible (pour lequel on a une expression exacte). Enfin, via la simulation numérique, une étude paramétrique est réalisée en fonction des nombres sans dimensions.Dans la troisième partie on présente une méthode numérique pour la simulation d'un modèle Vlasov-Boltzmann-Euler pour les sprays. Cette méthode couple le schéma VFFC à la méthode PIC (Particle In Cell). Les résultats présentés concernent l'écoulement d'un spray dans un pipeline courbe qu'on modélise par un système Vlasov-Boltzmann-Euler quasi-1D.This thesis contains three independent parts.The first part presents a proof of existence of weak global solutions to a Vlasov-incompressible-Navier-Stokes system with variable density. This system is obtained formally from a classical Vlasov-incompressible-Navier-Stokes model with fragmentation for which only two values for the particules radii are considered: a radius r1 for non fragmented particules and a radius r2<<r1 for particules created by fragmentation. The asymptotic model is obtained in the limit r2 vanishing.The second part deals with the modeling of a wave impact on a rigid wall. The purpose of our work is to study and model the escape of the gas between the liquid and the wall. In the numerical model we have replaced the liquid wave with a solid mass, and developed an ALE-VFFC code for the numerical simulation of the system. Scaling the system of equations allows us to obtain the dimensionless numbers governing the escape phenomena. The mean escape velocity is compared to the velocity in the case of incompressible gas. Finally, a parametric study with respect to the dimensionless numbers is carried out.We present in the third part the principles of the coupling between an efficient numerical method for hyperbolic systems (and non conservative equations arising in multiphase flows), namely the FVCF scheme, on the one hand; and a particle method for the Vlasov-Boltzmann equation (of PIC-DSMC type), on the other hand. Numerical results illustrating this coupling are shown for a problem involving a spray (droplets inside an underlying gas) in a pipe which is mcdeled by a 1D fluid-kinetic system