New lagrangian approach for wet plume modelling

Abstract : A new version of the lagrangian dispersion modelling system Micro-SWIFT-SPRAY (MSS developed by ARIA Technologies and ARIANET) has been developed in order to allow simulation of wet plume, microorganisms, insecticide or pesticide dispersion. For all these applications, it is necessary to take into account both gas and liquid phase evolution including mass and heat transfer. In the particular case of microorganisms distinct behaviors potentially occur when transported by the liquid and/or the gas phase. Following the MSS lagrangian approach, it is easy to define a mass quantity of vapor and a large number of droplets of the same diameter by a virtual particle. Hence a spectrum of different size of droplets can be model using several virtual particles. The development of the new module consists of modelling the physical phenomenon of evaporation and condensation inside a wet plume taking into account temperature and humidity of ambient atmosphere. Microphysics of droplet is solved using the classical laws of evaporation/condensation processes in the surrounding atmosphere. The calculated evaporation rate allows to estimate the diameter evolution and the temperature inside the droplet. The difficulty consists in characterizing the surrounding atmosphere. The interaction between droplets and ambient humidity has been performed on an eulerian frame. Two methods of two way coupling have been tested on academic cases (0D). The proposed paper will present the two approaches and the obtained results.