H15-117: Application of detached eddy simulation to neighborhood scale atmospheric dispersion
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Present work addresses the current important problem of modelling the dispersion of toxic gases (i.e. the wind field prognosis) released in the urban terrain or neighbourhood scale by a new for the area approach, the Detached Eddy Simulation. In this scale, both Fast Approximate (FAMs) and Fully Computational Models (FCMs) have been tested, while none of these models' categories can prevail over the other. Nevertheless, the FCMs are continuously becoming more user-friendly and approachable to the communities of researchers and decision-makers even though their use demands of high computational power and qualified personnel. Most often, such models are based on the Reynolds Average Navier-Stokes equations (RANS) and the Large Eddy Simulation approach (LES). Unfortunately, both methods result either to less accurate or most computationally expensive models. Therefore, it is necessary to seek a resolution that is intermediate between the RANS and LES models in order to find a better balance between efficiency and accuracy, like the hybrid RANS/LES or the DES models like the one in this work. Herein, a new model is presented, that is able to estimate the initial conditions of the source (e.g. a small explosion), as well as provide the needed spatial pattern of wind statistics and ultimately calculate the atmospheric dispersion of the gas. The model is utilizing the Detached Eddy Simulation approach, in conjunction with the one-equation turbulent Spalart-Allmaras method, in the problem of atmospheric dispersion. To implement this model, a new software called the Prognostic Model for Toxic Gases Dispersion was developed and is described here. Several selected software evaluation test cases have been conducted and compared with cases found in the literature using a set of proposed model acceptance criteria. In this paper some of this cases are presented.
