Abstract: Flood water in the accelerating section of a sediment-laden river is characterized by high sediment concentration, high flow velocity, and coarse particle sizes. Previous studies on the rheological properties of flood water focuses on high sediment concentration, ignoring the factor of high flow velocity, more preciously high shear rate. This study examines systematically the effects of sediment concentration, shear mode, temperature and salinity on the rheological properties of turbid water in the lower Yellow River under high velocity shear conditions. The results show that under high shear rates (≥ 1200 s-1 at the velocity of 3.6 m/s), the rheological properties of turbid water with sediment concentration of 106.6 - 957.8 kg/m3 follow the laws of Newtonian fluid, no yield stress is observed, and its apparent viscosity has an exponential relationship with sediment concentration. A temperature drop does not change its rheological properties but its apparent viscosity is increased, and lower temperature will result in a greater viscosity increase. At the same temperature, the gradient of viscosity increase is about several times to ten times that of clear water. A change in salinity has little effect on the apparent viscosity or rheological properties. The results are useful for further theoretical study of high velocity flow sediment carrying capacity and long-distance sediment transport.

Key words: turbid water, high-velocity shear, rheological properties, high concentration