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Numerical simulation of atmospheric dispersion : application for interpretation and data assimilation of pollution optical measurements

Abstract : Nowadays the control and surveillance of gas and particles emitted into the atmosphere is done more through optical systems, e.g. multi-spectral cameras, LIDARS, satellites images, etc. Optical instruments allow the measurement of pollutant concentration in the plume. It is believed that, in the future, optical instruments at high frequency resolution should work with or replace the current fixed and punctual monitoring networks. So they could contribute to a major technological leap in detecting substances in the atmosphere. In the industrial sector, the use of optical measurements could contribute to: A better knowledge of industrial sites. Management of the future regulatory controls, made through remote sensing addressed to measure COV and methane. Improvement of physical representability of dispersion models employed for prevention of major risks. An approach validated for critical environmental events. Recognition of emission sources. Current work is focused on the enhancement and interpretation of the results of optical measurements thanks to the numerical modelling of atmospheric dispersion. In order to make the most of the new experimental data, characterised by a high sampling frequency and a strong level of fluctuations, a robust direct simulation approach is required. It has to be able to capture not only the mean state of turbulent flow and of plume dispersion but also its higher moments, which better characterise the non-linear and instantaneous behaviour. The strategy of the present work is based on a gradual increment of complexity. Before dealing with the atmospheric dispersion and modelling methods to simulate higher moments, we treat the study of the Atmospheric Boundary Layer (ABL) and its simplest modelling strategy, such as the RANS model. Working with them, we have been faced with one big source of uncertainties: the boundary conditions, e.g. inflow profiles, ground roughness and others. The proper setting of boundary conditions enable to reduce numerical errors and correctly interpreted the final results. Although decades of studies, this issue is still open due to the extremely complexity of the ABL. Even the simple case of a Surface Boundary Layer (SBL) in neutral conditions can present difficulties due to the appropriate application of boundary conditions and the equilibrium of the coefficients of the turbulence models. Some cases from the literature are reproduced to understand the problem and apply the solutions suggested. This allowed to become familiar with cases encountered later on. Subsequently we pass to investigate the LES approach to model the SBL in neutral conditions together with the dispersion of a passive scalar and the related boundary conditions. The previous steps contribute to the development of a LES methodology employed to simulate numerically the atmospheric dispersion of a passive scalar. The development of the methodology has identified some physical and numerical criteria that could condition the validity and the accuracy of the approach adopted. In fact, the application of the criteria to simulate a wind tunnel experiment, conducted in the Laboratoire de Mécanique des Fluides et d’Acoustique of the École Centrale de Lyon, was useful to validate the LES methodology. The validation turned out to be more complex than expected because compromises were necessary to violate the fewest criteria. In this context, our methodology was validated with the appropriate interpretation of the results. Finally, all the acquired knowledge is used to simulate a real scenario, i.e. a test case of the TotalEnergies Anomaly Detection Initiatives (TADI) project, an experiment organised by TotalEnergies with the participation of different optical instruments manufacturers and developers. The numerical results are conceived in such way as to be able to interpret and assimilate the optical measurements. In particular using multi-spectral camera SIMAGAZ.
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Submitted on : Wednesday, July 27, 2022 - 10:49:12 AM
Last modification on : Friday, September 30, 2022 - 10:56:10 AM

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  • HAL Id : tel-03739279, version 1

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Jheyson Mejia Estrada. Numerical simulation of atmospheric dispersion : application for interpretation and data assimilation of pollution optical measurements. Other. Université de Lyon, 2022. English. ⟨NNT : 2022LYSEC012⟩. ⟨tel-03739279⟩

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