Energy consumption is one of the important indicators of green development. The pressure drop and the particle kinetic energy loss in the pipe bend result in high energy consumption of wheat pneumatic conveying. In this paper, the CFD-DEM method is used to study the characteristics of flow field in horizontal pipe bend. The results show that the particles converge together under the force of the curved pipe wall to form a particle rope. With increasing pipe bend ratio R/D, the aggregation of particle bundles becomes stronger and the particle spiral phenomenon decreases. The particles impact the pipe wall at an angular position of θ = 30–60° around the bend, and their velocity decreases slowly under the friction resistance of the pipe wall. The velocity loss caused by particles impacting on the pipe wall increases with increasing initial velocity. When the particle mass flow rate is 1.26 kg/s and the gas velocity is 10 m/s, the pressure drop in the bend decreases and then increases with increasing R/D. The pressure drop of the bend is smallest for R/D = 2 and increases gradually with increasing gas-phase velocity. With increasing of R/D, the wall shear force between the particles and the bending pipe decreases and then increases, and the position of the maximum force moves towards the bottom of the bending pipe. The area over which the wall shear force acts continues to decrease because of the aggregation of particle bundles. The research results provide a theory for optimal design and application of pneumatic conveying equipment for wheat particles.

Regional production-consumption imbalances and deficient multimodal connectivity in grain circulation systems have rendered traditional segmented transport inefficient, loss-intensive, and costly, constraining overall supply chain performance. In China, the persistent north-to-south and west-to-east grain transfer patterns, driven by regional production–consumption imbalances, have imposed significant challenges on the grain circulation system, making multimodal transport optimization a critical priority for national food security. Multimodal transport, a critical logistics optimization strategy, integrates diverse transport modes and hub nodes to enable end-to-end coordination, thereby enhancing circulation efficiency and food security. This study systematically reviews the transport configurations and modal characteristics of grain multimodal transport, and employs bibliometric analysis with the VOSviewer tool to map publication trends and keyword co-occurrence networks. Subsequently, recent advances in transshipment hub location selection and route optimization in multimodal transport systems are examined. Finally, existing technical bottlenecks are summarized, and future research directions are outlined from the perspectives of intelligent logistics, green and low-carbon development, coordinated operations, and supply chain resilience.

To investigate the motion mechanism and kinetic energy loss characteristics of wheat particles in a horizontal–vertical upward bend pipe, different curvature radii, gas velocities, and particle mass flow rates are used to study changes in particle velocity, the inter-particle contact force, and the particle–wall contact force in this study. The results indicate that larger curvature radii weaken the inter-particle contact force. The velocity difference between particles inside and outside of the bend first increases and then decreases at the elbow. Increasing the gas velocity increases the particle velocity and the particle–wall contact force. It also enlarges the velocity gap between the inner and outer particles of the bend, while weakening the inter-particle contact force. With an increase in the mass flow rate, the particle–wall contact force gradually rises at 0–30° of the bend, and then gradually falls at 30–90°. Meanwhile, the inter-particle contact force is enhanced. A higher gas velocity leads to a greater loss of particle kinetic energy caused by collisions. The velocity difference exhibited by particles on the inner and outer sides of the bend remains basically unchanged. The maximum inter-particle and particle–wall contact force is around the 30° bend angle.