Experimental Study on the Effect of the Parallel and Flake Ripple Bed Forms on the Manning Roughness Coefficient

Document Type : Technical Note


1 Associate Professor, Department of Water Engineering, Shahrekord University, Shahrekord, Iran

2 MSc. Student, Hydraulic Structures, Shahrekord University, Shahrekord, Iran

3 Assistant Professor, Department of Water Engineering, Shahrekord University, Shahrekord, Iran

4 Associate Professor Department of Civil Engineering, Amirkabir University, Tehran, Iran


Estimation of the flow resistance is one of the most important parameters in the planning, design and operation of water resources projects, including water transfer and river system management. Bed forms, such as ripple, have significant effects on total roughness. In this paper, the effects of two types of ripples on the Manning coefficient was investigated. Experiments were performed in the Hydraulic Laboratory of Shahrekord University. Some relationships were obtained based on the geometric characteristics of the ripple bed forms and flow conditions using SPSS software. It was also observed that in the case of parallel ripple bed form, the roughness was about 47% more than that of plane bed and in the case of flake ripple bed form, the increasing rate was 43%. It was concluded that the Manning coefficient was significantly affected by the parallel shape of ripple bed form compared with the flake shape.


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