Sediment transport in pipes is an effective engineering measure used to reallocate water–sediment resources and is widely used in reservoir flooding and sediment discharging, river dredging, floodplain area deposition, as well as other projects. An experimental investigation of sediment transport in pressurized pipes, with heterogeneous sediment (d₅₀ = 107 μm) of the lower Yellow River as the experimental material, is presented. This study mainly explored the change law of sediment transport and sorting in pressure pipes with an internal diameter of 0.08 m. The experimental results reveal that the presence of sediment significantly changed the distribution of the flow velocity field. At the same flow rate, the velocity of the lower water body with a high sediment concentration decreased, while that of the upper water body increased. At a low water flow rate, the increase in sediment concentration caused an asymmetric distribution of the cross-sectional velocity. The vertical concentration decreased in height, and the obvious stratification of vertical sediment particles was observed. With the increase in the flow rate, the asymmetry of the velocity distribution significantly decreased, the concentration profile tended towards being uniformly distributed along the vertical direction, and the separation effect of the sediment particles weakened.

As a new type of liquid discharged into the sea, concentrated brine exhibits complex mixing and stratification patterns due to changes in its density and hydrodynamic properties. This complexity impacts salinity transmission and can result in brine intrusion disasters, directly affecting both ecosystem and human life. This research adopted brine discharge into Dingzi Bay, Shandong Peninsula, a typical estuarine bay, as a case study. 3D convective diffusion numerical simulation techniques were applied to investigate the pathways, salinity rise, impact range, and overall effects on brine dispersal in marine water environments under the combined influence of river flow and tides. The results indicated the followings: (1) Significant spatial variations were observed in flow velocities within Dingzi Bay, with higher velocities near Xiang Island (where river flow turned into the bay) and at bay mouth; (2) The brine discharge point is influenced by complex hydrographic terrain and the combined effects of river flow and tidal movements, resulting in the formation of a high salinity area at the base of the discharge point, where salinity increases by more than 4 PSU within a 100-meter radius.; (3) During high tides, high-concentration brine was clearly transported upstream along the tidal channel, with a salinity increase of ≥3psu covering an area of 5.72×10⁴ m², extending up to 270 m upstream and 180 m downstream. Brine discharge led to significant mixing of concentrated seawater with seawater within the bay, altering the spatial and temporal distributions of salinity in Dingzi Bay and consequently affecting local sensitive marine species and water environment safety. This study systematically investigated the process of brine discharge into the ocean and its impact range. It was found that discharging brine in areas with higher currents promotes the mixing and dispersion of brine. Additionally, a seasonal discharge plan should be established to avoid discharges during periods of low runoff (such as winter) to minimize negative impacts on aquatic ecosystems and promote the health and diversity of marine ecosystems.

Piles are common support elements for marine and coastal structures. The scour around pile foundations caused by currents is a major threat to the stability and safety of these structures. The empirical equations commonly used for estimating the equilibrium scour depth around pile groups are limited in their predicative capability, especially when the current approaches the pile group at an angle. This study applies a Multi-Layer Perceptron Backpropagation (MLP/BP) neural network to develop a general model for predicting the local maximum equilibrium scour depth around pile groups in steady currents. The input parameters for the model include all relevant non-dimensional hydrodynamic and structural variables taking full account of the effects of the pile group arrangement and its orientation relative to the approaching current. The model’s performance was evaluated by comparing its predictions against those generated by multiple other machine learning methods, as well as against results from widely used empirical formulas. A comprehensive sensitivity analysis is carried out to determine the importance ranking of the input parameters on model accuracy.

A coupled CFD-DEM model was adopted to investigate the floating ice accumulation mechanism and its disturbance to the flow field in the pump house of coastal nuclear power plants in cold regions. Based on numerical simulations, the motion, accumulation, and flow interaction characteristics of floating ice under various release positions and heights were analyzed. The results indicate that the release height significantly governs the accumulation morphology and hydraulic response. The release height critically determines ice accumulation patterns and hydraulic responses. For inlet scenarios, lower heights induce a dense, wedge-shaped accumulation at the coarse trash rack, increasing thickness by 57.69% and shifting the accumulation 38.16% inlet-ward compared to higher releases. Conversely, higher releases enhance dispersion, expanding disturbances to the central pump house and intensifying flow heterogeneity. In bottom release cases, lower heights form wall-adhering accumulations, while higher releases cause ice to rise into mid-upper layers, thereby markedly intensifying local vortices (peak intensity 79.68, approximately 300% higher). Spatial release locations induce 2.7–4.8-fold variations in flow disturbance intensity across monitoring points. These findings clarify the combined impact of the release height and location on the ice accumulation and flow field dynamics, offering critical insights for the anti-ice design and flow safety assessment of pump houses.

The shallow-buried abandoned Yellow River Delta (893–1855 AD) exhibits a distinctive geomorphic system shaped by coupled fluvial sediment reduction, climatic transition, and relative sea-level fluctuations, with its intact deposits recording key temperate delta evolution during climate change. Using four sediment cores, we applied optically stimulated luminescence (OSL) dating, sedimentary facies analysis, and grain-size techniques (C-M diagram, end-member modeling), integrated with geomorphic interpretation and historical data, to reconstruct the delta’s evolutionary sequence and clarify storm surge-driven geomorphic reworking and its diagnostic indicators. Results indicate that the delta’s evolution was governed by abrupt fluvial sediment loss, intensified storm dynamics, and relative sea-level rise. The 893 AD Yellow River avulsion triggered delta abandonment (893–1482 AD), driving a shift from a fluvially dominated muddy coast to a wave-controlled sandy system. Sandy deposits initially formed at M04A and prograded landward to M03A. During the Little Ice Age (1482–1855 AD), frequent storm surges further expanded and elevated these sandy accumulations, while weak sedimentation persisted in the inland depression (B03). This differential process generated a unique plain lowland–coastal highland system, a rare geomorphic type among large river deltas that differs from classic island–continent and barrier–lagoon systems. This study elucidates the phased response of temperate monsoon abandoned deltas to millennial-scale climate change, advances theories of multi-factor coupled delta evolution, and provides scientific support for coastal protection, stability assessment, and evolutionary prediction under global warming.