Effects of canopy frontal and plan solidities on the momentum roughness parameters

Abstract: Experiments were conducted to characterise the momentum roughness parameters of flow over canopies with a range of frontal and plan solidities. The canopies were generated using cylindrical, conical and inverse conical elements. Five sets of plan solidities, each consisting of three frontal solidities accounting for the three element shapes, were modelled. A hotwire probe was used to measure the velocity profile within and over the canopy, which was used to determine the roughness length and displacement height for each canopy. The results showed that at a fixed plan solidity, the increase of frontal solidity had negligible impact on the roughness length, while the displacement height increased. This trend, observed for cylindrical and conical elements, differs significantly from that found in the literature for canopies made of cuboidal elements, and highlights the impact of the shape of the canopy elements on the flow and the momentum roughness parameters. Keywords: canopy flow, boundary layer flow, momentum roughness length