Regularity of transportation for cohesive bank-collapsed materials

The transportation of bank-collapsed materials is a key issue among river evolution processes. In this study, a series of flume experiments were conducted to monitor riverbank collapse processes and to explore the regularity of transportation for cohesive collapsed materials. The collapsed materials, both the bed and suspended loads, that transformed from collapsed materials were intensively evaluated under experimental conditions. The results showed that the collapsed materials contributed to 12～20 % sedimentation in situ, 8～14 % suspended loads and 70～80 % bed loads. In addition, the bed load motion efficiency coefficient (eb), suspended load motion efficiency coefficient (es) and sediment carrying capacity factor (U3/gRω) were introduced to describe the transportation of collapsed materials in terms of energy dissipation. This research provides theoretical and practical benefits for predicting channel evolution processes.

Research on the Wing-Type Antiscour Device of Pier Based on Scour Test and Numerical Simulation

In order to reduce the local scour before the antiscour device of piers, this paper proposed an improvement on a “V-type” device. That was to say, wing plates were set on the surface of the “V-type” device to enhance the diversion and reduce the local scour. To explore the protection effect of the modified device, the inclination angles of the wing plates were set to three angles, and the scour characteristics around the device were studied through the flume scour test and numerical simulation test. The results showed that the wing plates can reduce the impact force of the diving flow which was at the front end of the protective device. Besides, they could also disturb the flow around both sides of the device and weaken its sediment carrying capacity. Thus, the local scour around the device was effectively reduced. Especially, when the wing plates were 30°, the performance of reducing the local scour was the best.

Influence of wave and current flow on sediment-carrying capacity and sediment flux at the water–sediment interface

In nearshore waters, spatial and temporal scales of waves, tidal currents, and circulation patterns vary greatly. It is, therefore, difficult to combine these factors’ effects when trying to predict sediment transport processes. This paper proposes the concept of significant wave velocity, which combines the effects of waves, tides, and ocean currents using the horizontal kinetic energy superposition principle. Through a comparison of the relationship between shear stress at the water–sediment interface and sediment-carrying capacity, assuming equilibrium sediment flux, a new formula for sediment-carrying capacity, which incorporates the concept of significant wave velocities, is derived. Sediment-carrying capacity is a function of the critical velocity, which increases with water depth and decreases with increasing relative roughness of the seabed. Finally, data from field observation stations and simulations are used to test the proposed formula. The results show that the new formula is in good agreement with both field and simulation data. This new formula for sediment-carrying capacity can be used to simulate nearshore sediment transport.

Determination of the Sediment Carrying Capacity Based on Perturbed Theory

According to the previous studies of sediment carrying capacity, a new method of sediment carrying capacity on perturbed theory was proposed. By taking into account the average water depth, average flow velocity, settling velocity, and other influencing factors and introducing the median grain size as one main influencing factor in deriving the new formula, we established a new sediment carrying capacity formula. The coefficients were determined by the principle of dimensional analysis, multiple linear regression method, and the least square method. After that, the new formula was verified through measuring data of natural rivers and flume tests and comparing the verified results calculated by Cao Formula, Zhang Formula, Li Formula, Engelung-Hansen Formula, Ackers-White Formula, and Yang Formula. According to the compared results, it can be seen that the new method is of high accuracy. It could be a useful reference for the determination of sediment carrying capacity.

The Analysis and Discussion of Sediment Transport Capacity Formula

Combined with the equilibrium condition, the formula of vertical average sediment concentration has been derived from the vertical two-dimensional suspended sediment diffusion equation. Based on analyzing and comparing two hydrodynamic formulas, a new formula of sediment carrying capacity has been deduced. Some river and inshore sediment data has been collected to validate the formula and find that the new formula has higher accuracy and applicability comparing with the two hydrodynamic formulas, it shows that the new formula has a high application value.

Preliminary Study about the Sediment Carrying Capacity Formula

Combined with the equilibrium condition, the formula of vertical average sediment concentration has been derived from the vertical two-dimensional suspended sediment diffusion equation. Based on analyzing and comparing two hydrodynamic formulas, a new formula of sediment carrying capacity has been deduced. Some river and inshore sediment data has been collected to validate the formula and find that the new formula has higher accuracy and applicability comparing with the two hydrodynamic formulas, it shows that the new formula has a high application value.