A novel explicit modeling framework based upon correlated Random Field and Level-Set methods is presented and applied to cement paste hydration. Focus is then made on effective diffusive properties prediction through numerical homogenization, using the Lattice Boltzmann Method (LBM), exploring the stability limits and performance of this method for heterogeneous media.RÉSUMÉ. Une méthode originale de création de morphologies de pâtes de ciment en cours d'hydratation à l'aide d'excursions de champs aléatoires corrélés est introduite. On présente ensuite le calcul des propriétés diffusives effectives homogénéisées de ces pâtes à l'aide de la Méthode de Boltzmann sur gaz réseau, les limites de stabilité et de performances associées à cette méthode pour les matériaux hétérogènes, ainsi qu'une application aux pâtes de ciment en cours d'hydratation
This work is centered on the safe usage of the lattice Boltzmann method for 2-D pure diffusion. The basics of the method for pure diffusion are first elucidated using a new definition given in the paper. The oscillating behavior and safe conditions of use are then explored in the case of homogeneous material as well as heterogeneous materials with circular and plane interfaces. As a conclusion, the range of valid relaxation factors is given for a correct use of lattice Boltzmann method.
This work proposes an estimation of the possible heat recovery of self-heating compost piles for building applications. The energy released during the aerobic composting of lignin and cellulose-based materials is computed by solving an inverse problem. The method consists first in an experimental phase with measurement of the temperature within the heap, then a numerical procedure allows for the inverse identification of the heat production due to the chemical reaction of composting. The simulation results show a good accordance with the experiments for the chosen source-term model. Comparing the results to the theoretical values for the energy released by aerobic composting provides an estimate for the efficiency of the reaction. The reached temperatures and recovered energy fit with the order of magnitude of building needs.
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