Author(s): Shuyou Cao; Kejun Yang; Xingnian Liu
Keywords: Compound channels; Composite roughness; Relative error; Momentum transfer
Abstract: Composite roughness is an important parameter in hydraulic calculation of compound channels. Five representative methods predicting composite roughness are systematically summarized in the paper, including methods by Pavlovskij, Einstein-Banks, Lotter, Krishnamurthy-Christensen, and Dracos-Hardegger. Two hundred seventy seven experimental data and field data are applied to verify the validity of those methods. Comparison and analysis of those methods show that those methods are not fit well to assess the composite roughness in compound channels. The main reason lies on the facts that the momentum transfer is neglected in approaches of PM, HEM, LM and KCM. On the other hand, DHM method is better, but basically is an empirical approach and has no universality in spite of its considering momentum transfer.