Direct measurement of bottom shear stress under high-velocity flow conditions

• We directly measured the bottom shear stress under high-velocity flow conditions.
• We built a laboratory-scale flume to achieve high-velocity flow conditions.
• We estimated the flow resistance by simultaneously measuring flow velocity and bottom shear stress.

The objectives of the present research are to accurately measure bottom shear stress under high-velocity flow conditions. To achieve high-velocity flow conditions, a laboratory-scale flume has been specially built in which flow velocity can reach over 3 m s−1. Also an instrument that can directly measure bottom shear stress has been developed and validated. Then, the flow resistance has been estimated by simultaneously measuring flow velocity and bottom shear stress. It appears that the shear stress is indeed proportional to velocity squared and also to Reynolds number. On the other hand, Manning's n value and the skin friction factor are more or less uniform across all experimental cases.