A Numerical Investigation of Flow and Scalar Dispersion within 3x3 Building Arrays

Flow and passive scalar dispersion within 3x3 building (block) arrays are numerically investigated using a Reynolds-averaged Navier-Stokes equations (RANS) model with the k-ε turbulence closure scheme based upon the renormalization group theory. Two 3x3 array configurations are considered: an array of 9 cubical blocks, and an array of 8 cubical blocks and double-height central block. Simulated flow fields in both configurations are validated against the data obtained from water channel experiments. Although lateral inflow in the 2nd column of the array is weak in the numerical experiment, general flow features observed in the water channel experiment (e.g., divergence in front of central block, lateral channeling, wake flow) are well simulated in both configurations. Portal vortices and streamlines confirming lateral channeling are revealed within the uniform-height block array. In the case of the central block being higher than other blocks, downdraft in front of central block induces stronger divergence and lateral outflow in the 1st column of the array. This is also responsible for stronger lateral inflow in the 2nd column. The lateral outflow in the 1st column disrupts streamwise channeling flow and scalar dispersion, resulting in higher and lower concentration of scalar in the 1st and 2nd column, respectively. Further analyses are made on the flow and scalar fields in the wake region.