Experimental Study of the Roughness Parameter of Channel

Abstract

【Background and objective】 The transport capacity of a channel depends on a multitude of factors, of which channel roughness is an important one. Currently, there is a lack of study on how to choose the roughness parameter in channel design, and the purpose of this paper is to plug this gap, systematically studying the relationship between the roughness parameter and other factors. 【Method】 The study was based on experiments, from which we measured the hydraulic characteristics of channels under different water flow rates. The relationship between the hydraulic characteristics and the factors that affect transport capacity of the channels were analyzed. 【Result】 ①The water surface curve and water flow rate in the channel are nonlinearly related. ②When the slope of the channel bed is the same, water flow velocity decreases along the channel. Thus, to keep channel function properly, its bed slope should increase and roughness decreases. ③The value of the roughness parameter depends not only on the lining materials of the channel but also on water flow in that the roughness parameter decreases in fast-flow sections while increases in slow-flow sections. We also found that the relationship between water depth and water discharge rates could become nonlinear in some sections; channel design should consider geometrical shapes of the cross-sections by either physical simulation or theoretical calculation. 【Conclusion】 The roughness parameter of channel depends on many factors and should be determined based on water flow pattern, how the channel was constructed, as well as its serving history. For the experiment we studied, the roughness parameter increased from 0.008 when water flow rate was (2.41×2)×10-3 m3/s to 0.0085 when the flow rate reduced to (2.41× 0.9)×10-3 m3/s.

Keywords

• weir discharge
• frictional water head loss
• cross-section average water velocity of cross section
• roughness