Impulse concept in formulating a unified approach to bedload transport

Due to their stochastic and fluctuating nature, the entrainment and transport of sediment particles present great challenges to scientists and engineers who endeavor to formulate a universal framework for quantifying sediment dynamics and transport behaviors. The application of impulse theory represents one of such efforts and has received increased attention over the past decade. Practically, the impulse concept helps to remove the inactive periods of transporting process from the entire transport history, such that the underlying driving mechanism of particle movements can be better identified. This approach not only proves to be useful in characterizing the threshold of motion conditions, as tested against experimental data from an increased body of literature, but also provides a new perspective in formulating the constitutive relation of bedload transport. In this study, we employ a similar criterion, yet based on the pertinent amounts of energy imparted upon sediment particles, to reproduce the stress-transport relations. These post-conditioned stress-transport relations are almost devoid of the inactive periods and, thus, better represent the physics of transport of sediment particles. It is noted that a consistent 1.5th power law has been recovered from a wide range of transport flow conditions, which can be deemed as a constitutive relation for bedload transport. Further examination of these data sets indicates that, in essence, the obtained 1.5th power relation accounts for a constant energy transfer efficiency of fluid flow applied upon the sediment particles. These efforts, based on the impulse concept, lead to a unified approach to sediment transport problems.