CFD Modeling of Pollution Dispersion in Building Array: Evaluation of turbulent scalar flux modeling in RANS model using LES results

Modeling of turbulent scalar flux in CFD (Computational Fluid Dynamics) for near-field dispersion around buildings is examined by investigating both velocity and concentration fields obtained by two modeling approaches, i.e., RANS RNG k-e and LES. A building array model with a point source located in between the central buildings is adopted as a target configuration. First, the prediction accuracy of LES is confirmed by comparing with the RNGcomputation and the results from an experiment conducted by the authors. LES gives better results than RNG, in terms of time-averaged velocity and concentration distribution in comparison with the wind tunnel experimental results. Next, the eddy viscosity and the eddy diffusivity are determined by LES data using a least square approach as suggested in the dynamic sub-grid scale model. Large differences can be observed between the distributions of the estimated eddy viscosity by using LES data and the eddy diffusivity obtained by RNG, since the eddy diffusivity is not always proportional to the eddy viscosity.

[1]  D. Lilly,et al.  A proposed modification of the Germano subgrid‐scale closure method , 1992 .

[2]  M. Antonopoulos-Domis,et al.  Large-eddy simulation of a passive scalar in isotropic turbulence , 1981, Journal of Fluid Mechanics.

[3]  Yoshihide Tominaga,et al.  AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings , 2008 .

[4]  E. R. V. Driest.  On Turbulent Flow Near a Wall , 1956 .

[5]  S. Murakami,et al.  COMPARISON OF VARIOUS TURBULENCE MODELS APPLIED TO A BLUFF BODY , 1993 .

[6]  T. G. Thomas,et al.  Mean Flow and Turbulence Statistics Over Groups of Urban-like Cubical Obstacles , 2006 .

[7]  A. Martilli,et al.  Comparison Between Large-Eddy Simulation and Reynolds-Averaged Navier–Stokes Computations for the MUST Field Experiment. Part II: Effects of Incident Wind Angle Deviation on the Mean Flow and Plume Dispersion , 2010 .

[8]  Gianluca Iaccarino,et al.  Numerical simulation of scalar dispersion downstream of a square obstacle using gradient-transport type models , 2009 .

[9]  Bert Blocken,et al.  CFD simulation of near-field pollutant dispersion on a high-resolution grid : a case study by LES and RANS for a building group in downtown Montreal , 2011 .

[10]  Yoshihide Tominaga,et al.  Turbulent Schmidt numbers for CFD analysis with various types of flowfield , 2007 .

[11]  A. Martilli,et al.  Comparison Between Large-Eddy Simulation and Reynolds-Averaged Navier–Stokes Computations for the MUST Field Experiment. Part I: Study of the Flow for an Incident Wind Directed Perpendicularly to the Front Array of Containers , 2010 .

[12]  Y. Tominaga,et al.  Numerical simulation of dispersion around an isolated cubic building: Model evaluation of RANS and LES , 2010 .

[13]  S. Orszag,et al.  Development of turbulence models for shear flows by a double expansion technique , 1992 .

[14]  Minoru Mizuno,et al.  Numerical flow computation around aeroelastic 3D square cylinder using inflow turbulence , 2002 .

[15]  Yoshihide Tominaga,et al.  CFD modeling of pollution dispersion in a street canyon: Comparison between LES and RANS , 2011 .

[16]  J. Smagorinsky,et al.  GENERAL CIRCULATION EXPERIMENTS WITH THE PRIMITIVE EQUATIONS , 1963 .

[17]  Riccardo Buccolieri,et al.  Numerical simulation of atmospheric pollutant dispersion in an urban street canyon: Comparison between RANS and LES , 2011 .

[18]  Rex Britter,et al.  Simulations of pollutant dispersion within idealised urban-type geometries with CFD and integral models , 2007 .

[19]  Theodore Stathopoulos,et al.  Numerical evaluation of pollutant dispersion in the built environment: comparisons between models and experiments , 2008 .

[20]  H. Werner,et al.  Large-Eddy Simulation of Turbulent Flow Over and Around a Cube in a Plate Channel , 1993 .

[21]  Theodore Stathopoulos,et al.  Near-field pollutant dispersion in the built environment by CFD and wind tunnel simulations , 2011 .

[22]  Jan Carmeliet,et al.  Evaluation of the ventilation potential of courtyards and urban street canyons using RANS and LES , 2011 .

[23]  Caskey,et al.  GENERAL CIRCULATION EXPERIMENTS WITH THE PRIMITIVE EQUATIONS I . THE BASIC EXPERIMENT , 1962 .

[24]  Michael Schatzmann,et al.  Issues with validation of urban flow and dispersion CFD models , 2011 .

[25]  Yoshihide Tominaga,et al.  Numerical simulation of dispersion around an isolated cubic building: Comparison of various types of k–ɛ models , 2009 .

[26]  S. Murakami,et al.  Comparison of various revised k–ε models and LES applied to flow around a high-rise building model with 1:1:2 shape placed within the surface boundary layer , 2008 .

[27]  B. Blocken,et al.  CFD simulation of pollutant dispersion around isolated buildings: on the role of convective and turbulent mass fluxes in the prediction accuracy. , 2011, Journal of hazardous materials.

[28]  Masud Behnia,et al.  Reynolds averaged simulation of unsteady separated flow , 2003 .

[29]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[30]  Ken-ichi Abe,et al.  Towards the development of a Reynolds-averaged algebraic turbulent scalar-flux model , 2001 .