Geometry of a flue organ pipe with a closed pipe of 141.5 mm in length (Reference model). (a) 3D view of the model with an outer region. The length, height and width of the inlet are taken as l_in = 50 mm, h_in = 3 mm and w_in = 10 mm, respectively. (b) Dimensions of the edge, flue with chamfers and foot channel on the 2D cross-section: h_p = 20 mm, l = 4 mm, θ = 20°, w_cf = 0.71 mm, h_f = 1 mm, l_f = 3 mm, h_cb = 20.8 mm, R = 19.8 mm, h_e = 2.51 mm and h_t = 1.71 mm; the widths of the pipe and foot are taken as w_p = 20 mm and w_cb = 20 mm, respectively.