Vertical distribution characteristics and concentration predictive equation of suspended sediment driven by pneumatic desilting

Localized sediment siltation poses a major engineering challenge that restricts the operational safety of water-related infrastructure, such as coastal ports and pile-supported wharfs. Pneumatic jet desilting technology provides a new solution for this problem. By combining stratified suspended sediment sampling with high fidelity particle image velocimetry (PIV) measurements, four transient dynamic stages of bed sediment suspension are identified. Furthermore, the vertical distribution characteristics of non-uniform sediment are quantified. The results show an energy saturation effect during the transfer of gas kinetic energy to the water body. The vertical flow velocity in the core region follows a power-law relationship with the incident gas flow rate. In the multiphase flow field, the distribution of non-uniform particles is governed by the mechanical competition between turbulent entrainment in the bubble wake and gravity settling. This competition leads to vertical spatial sorting. Based on the multiphase kinetic energy dissipation mechanism, a dimensionless generalized suspension index is constructed. Consequently, a predictive equation for the vertical concentration distribution of suspended sediment under pneumatic jets is derived. This equation theoretically reveals the spatial distribution laws of sediment under submerged gas jets. The equation provides an analytical basis for parameter optimization and energy control in pneumatic desilting engineering.