A combined fully-resolved and porous approach for building cluster wind flows

Abstract

In wind flow simulations, a full resolution of all the buildings in a large city is difficult to achieve due to the constraints on computing power. This paper explores a possible approach to modeling part of the urban built area as a porous medium, while fully resolving the areas of the targeted buildings for analysis. We refer to this approach as the mixed model, and we have evaluated it by comparisons with other generally used simulation methods. In all of the three cases we examined, the central section, including the targeted buildings, was fully resolved, and the two adjacent areas were modeled in one of the following three ways: (1) fully resolved (the B&B case, which was assumed to be the most accurate), (2) modeled as a porous medium (the P&B case, which was our proposed mixed model), or (3) modeled with roughness height (the C&B case, which has been the most commonly adopted approach). We found that the P&B case predictions were more efficient and accurate than those of the C&B case, and they required less computer power than the B&B case, but had similar accuracy to predictions from the B&B case. These results show that the new mixed modeling approach presents the possibility of simulating the entire city by using porous turbulence models that requires no more than the currently available computational capability, thereby expanding the scope of simulations without losing the main characteristics of the target area.