Experimental Study on the Influences of Channel Width on Live-bed Scour at Submerged Weirs

Two sets of experiments were carried out in two sand-recirculating flumes with different widths (0.44 m and 1.54 m), investigating the effects of channel width on live-bed scour at submerged weirs. All the experiments were conducted using the same sand (uniform sand, median grain size d₅₀ = 0.85 mm), weir height z = 30 mm and tailwater depth h_t = 150 mm over a range of approach velocities under live-bed scour conditions. The experimental results show that the upstream scour at the submerged weir in the big flume is significantly deeper than that in the small flume. This is attributed to the different approach bedform sizes formed in two flumes as the measured approach bedform height in the big flume is approximately two times of that in the small flume. The data also show that the downstream scour depth is greater in the big flume. This is due to the stronger three-dimensionality in the downstream scour hole caused by the more three-dimensional approach dunes observed in the big flume.