Flow resistance in gravel bed open channel flows case: intense transport condition

Abstract

Gravel bed can be categorised into three bed load conditions, i.e. no load, moderate and intense. An experimental investigation was carried out in an open channel flow with gravel bed surface of grain size of D₅₀ values 6.5 mm intense load conditions. The investigation of the roughness characteristics of gravel bed open channel flows under intense load conditions over various discharges and flow depths are presented. Variation of friction factor for the roughness conditions for different flow depths is estimated. The intensity of the bed load is calculated with the help of sediment transport rate. The bed load transport rate for the intense load conditions is also determined from experimentation on gravel beds of 6.5 mm gravel size for different flow depths. Using the data-set of other researchers and present experimental data, a new model as a function of intensity of the bed load transport with respect to Shield’s parameter is formulated. The modified model gives satisfactory results as compared to previous works, which is displayed through error analysis.

Keywords:

• Gravel bed open channel
• Darcy–Weisbach friction factor
• bed load
• sediment transport
• Shield’s parameter
• boundary shear stress

Acknowledgement

The encouragement and assistance from the Institute and the Research project by the second authors for carrying out the research work in the Hydraulics laboratory at National Institute of Technology, Rourkela is gratefully acknowledged.