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The purpose of this work is to model turbulent Taylor-Couette-Poiseuille flows submitted to a temperature gradient. These flows are relevant in many industrial applications including rotating machineries and more especially for the effective cooling of electric motors. Several turbulence closures (k-ω SST, RSM and LES) are first compared in the isothermal case and validated against the reliable experimental data of Escudier and Gouldson [1]. A detailed analysis of the coherent structures within the boundary layers is proposed. The model offering the best compromise between computational cost and accuracy is then used to perform more computations in the configuration with a temperature gradient considered by Kuosa et al. [2]. In their system, the air flow enters the rotor-stator cavity radially. Correlations for the average Nusselt numbers along the rotor and stator as a function of the control parameters (rotation rate, air flow rate, Prandtl number) are provided and compared with data available in the literature [3].

A monopropellant system is one of the propulsion system types used in space which uses a single substance that reacts or decomposes by itself to a hot gas, releasing energy in the form of heat. This system has medium performance where the specific impulse range is between 130 and 225 seconds. The hydrazine liquid is the most used for monopropellant systems because it gives a good performance. However, hydrazine is a very toxic and inflammable substance that has an implication on the security of the persons during testing of the system. In addition, its freezing point is around 1.5 °C which can induce thermal problems during the spacecraftʼs mission. An alternative solution is to use hydrogen peroxide known as green propellant, which can be stored as liquid, and has high density level. An investigation and studies have been performed to develop new hydrogen peroxide monopropellant thrusters for application in the future satellites. The decomposition technology of hydrogen peroxide has been also used for the development of bipropellant and hybrid rocket engines. This paper presents the design, performances and tests of a one newton hydrogen peroxide monopropellant thruster. The test results obtained show that the monopropellant thruster gives good performances where the specific impulse is around 170 seconds.

The present study focuses on the combustion of liquid propellants used in engines for space propulsion applications (satellites and launch vehicles). The combustion of the following propellant combinations was studied: hydrogen/oxygen, hydrocarbon fuel/oxygen, hydrocarbon fuel/hydrogen peroxide, hydrazine/nitrogen tetroxide, Mono-methyl hydrazine/nitrogen tetroxide and Unsymmetrical dimethyl hydrazine/nitrogen tetroxide. The purpose of this paper is to determine the combustion flame temperature and the other thermochemical parameters (combustion products politropic parameter and molecular mass) as function of mixture ratio by mass of oxidizer to fuel (O/F). Furthermore, the vacuum specific impulse was also calculated at assumed pressure conditions of propulsion engines to show the effect of mixture ratio of the propellants on the performances. For the determination of the equilibrium composition at assumed temperature, nonlinear systems of equations were solved numerically using Lieberstein’s method. Some results were presented and compared with previous research in this area, the comparison shows good agreement between the results and the difference is less than 5%. As example, three cases of bi-propellant engines were studied using the programs of combustion and frozen fluid flow approximation: Space Shuttle Main Engine (SSME), Zenit second stage engine (RD-120) and Ariane-5 upper stage engine (Aestus).

This study aims to corroborate experimental studies in mechanical alloying by theoretical studies, particularly the calculation of the contact temperature at the impact point of the balls, basing on the mathematical model of a compact powder between two colliding balls. Indeed, within this study, we show the influence of some geometrical, dynamic, and thermophysical parameters on the variation in the contact temperature of balls and Al and Ti powders inside a vial of planetary ball mill.

International audience; no abstract

This paper is based on dust aerosol cycle modelling in the atmospheric model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) coupled with the EXternalised SURFace scheme SURFEX. Its main goal is to create an appropriate mineral dust emission parameterization compatible with the global database of land surface parameters ECOCLIMAP, and the Food and Agriculture Organization (FAO) soil type database in SURFEX. An improvement on the Dust Entrainment And Deposition scheme (DEAD) is proposed in this paper by introducing the geographical variation of surface soil size distribution, the Marticorena and Bergametti (1995) formulation of horizontal saltation flux and the Shao et al. (1996) formulation of sandblasting efficiency α. To show the importance of the modifications introduced in the DEAD, both sensitivity and comparative studies are conducted in 0 dimensions (0-D) and then in 3 dimensions (3-D) between the old DEAD and the new DEAD. The results of the 0-D simulations indicate that the revised DEAD scheme represents the dust source emission better, particularly in the Bodélé depression, and provides a reasonable friction threshold velocity. In 3-D simulations, small differences are found between the DEAD and the revised DEAD for the simulated Aerosol Optical Depth (AOD) compared with the AErosol RObotic NETwork (AERONET) photometer measurements available in the African Monsoon Multidisciplinary Analyses (AMMA) databases. For the surface concentration, a remarkable improvement is noted for the revised DEAD scheme.

This paper is based on dust aerosol cycle modelling in the atmospheric model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) coupled with the EXternalised SURFace scheme SURFEX. Its main goal is to create a global mineral dust emission parameterization compatible with the global database of land surface parameters ECOCLIMAP and the Food and Agriculture Organization (FAO) soil type database in SURFEX, based on both Shao (1993) and Marticorena and Bergametti (1995) parameterizations. An arrangement on the Dust Entrainment And Deposition scheme (DEAD) is proposed in this paper by introducing the geographic variation of surface size distribution, the Marticorena and Bergametti (1995) formulation of horizontal saltation flux and the Shao (2001) formulation of sandblasting efficiency α. To show the importance of the modifications introduced in the code DEAD, both sensitivity and comparative studies are realized in 0 dimensions (0-D) and then in 3 dimensions (3-D) between the old DEAD and that developed in this paper. The results in the 0-D simulations indicate that the developed DEAD scheme represents the dust source emission better, particularly in the Bodélé depression and provides a reasonable friction threshold velocity. In 3-D simulations, small differences are found between the DEAD and developed DEAD schemes for the simulated Aerosol Optical Depth (AOD) compared with the photometer AErosol RObotic NETwork (AERONET) measurements available in the African Monsoon Multidisciplinary Analyses (AMMA) databases. But, for the surface concentration a remarkable improvement is noted for the developed DEAD scheme.