Abstract
The macroscopic drag-force model for urban/forest/vegetation canopy flows has a bottleneck in providing an appropriate set of model drag coefficients CD to the canopy layer, even if its geometrical structure is quite simple. To resolve the issue, the authors have recently explored an approach, in which the preliminary analysis, a direct simulation of canopy flow, is carried out in advance to the macroscopic model prediction (main analysis) to obtain a proper CD profile for the target problem. To introduce the dependence of the model coefficient on the spatial resolution employed in the main analysis explicitly, this paper introduces two modifications to the approach:(i) A low-pass spatial filtering whose size is comparable to the grid resolution of the main analysis is performed to the results of the preliminary analysis, and (ii) not just CD but λCD, where λ denotes the canopy density, is estimated together from the smeared out data. Applicability of the modified approach is demonstrated in an open-channel flow with patched vegetation zones.
