ETUDE NUMERIQUE DE LA DISPERSION D’UN SCALAIRE PASSIF EN MILIEU URBAIN SIMPLIFIE

Abstract

The objective of this thesis is the numerical study of the dispersion of a passive scalar urban simplifies using the Shensi computer code by comparing the experimental results from the University Hamburg (Experience in MUST (Mock Urban Setting Test)). The work is to exploit the experimental data obtained in atmospheric wind tunnel on a physical model of the site of the campaign MUST (Mock Urban Setting Test) in order to assess the CHENSI calculation model in 3D, developed by the team dynamics Atmospheric Inhabited LMF / ECN. The code is based on the standard model (k-ε) of Launder and Spalding [1]. For the integration of Equations Differentials Potential (EDP) forming the mathematical model, the finite volume method Peric and Ferziger [2] was used with the offset arrangement of unknown MAC (Marker And Cell) Harlow and Welch [3] Discretize terms PDE. The boundary conditions are imposed according to wall laws (ground and on buildings) or Dirichlet condition (entry borders) or Neuman (output border or upper limit). The digital domain used is comparable to that of the blower of experience with a three-dimensional Cartesian grid. Numerical results are presented for the characteristics of the medium flow (U, W), to the turbulence of kinetic energy (TKE) and the concentration field of a passive scalar (C), along two directions of incidence of wind (0 ° - 45 ° relative to the axis of the street). To compare objectively the performance of Shensi model with those of other European codes also used to simulate MUST configuration, statistical indicators proposed by Chang and Hanna [4] were calculated. For both directions of the incident wind, the analysis shows that the results for the mean flow fairly reflect physical reality. It notes, however, that the kinetic energy of turbulence is underestimated compared to values measured in the wind tunnel. The average field concentration is in good agreement with that obtained experimentally.