An experimental study of pressure distributions within an air-permeable, double-layer roof system in regions of separated flow

This paper is concerned with the pressure distributions on the external and internal surfaces of the outer layer of an air-permeable, double-layer roof system placed on a low-rise building in a region of separated flow. In particular, the effects of the gaps between panels (G), cavity depth between layers (H), and the panel size (L) on the pressures and panel loads are examined. Wind tunnel-based experimental data from the model of a low-rise building in an open country terrain were used. In total, 39 configurations were examined for the range 1/30≤G/H≤30 and 0.53≤t/G≤16, where t   is the panel thickness. It was found that the cavity pressure distributions are significantly affected by the geometric parameters. Values of the non-dimensional parameter, ϕ=[G/H]2[(fHLc/H)/(2(CL+ftt/G))] >~1 are associated with the cavity flow resistance controlling the pressure drops, leading to reduced-magnitude peak panel loads. The implications of the results for model-scale wind tunnel testing are discussed.