Hydraulic transportation of the piped carriage is a new energy-saving and environmentally-friendly transportation mode. There are two main states in the conveying process, stationary and moving. In the process of hydraulic transportation of the piped carriage, the study of the stress of the water flow act on the cylinder wall of the piped carriage can help to improve the design of the piped carriage structure and even the selection of piped carriage materials. The distribution of flow velocity around the stationary piped carriage and the stress distribution on the cylinder wall of the stationary piped carriage were investigated by combining numerical simulations with model experiment verification. The commercial finite element software, Comsol Multiphysics, was utilized to solve this problem using the arbitrary Lagrangian–Eulerian (ALE) method. The results showed that the simulation results were in good agreement with the experimental results. It also showed that the ALE method can well be applied for fluid-structure problems in the process of hydraulic transportation of the piped carriage. The simulation results showed that the low velocity region near the inner wall of the pipe was smaller than that near the outer wall of the piped carriage, and both regions decreased with the increase of the discharge. The maximum stress on the cylinder wall of the piped carriage appeared between the two support feet in the middle and rear sections of the cylinder. The influence of the unit discharge on wall stress increased with the increase of the discharge, that is, k₁ < k₂ < k₃. Moreover, the increase of the discharge had the greatest influence on the circumferential component of the principal stress of the cylinder, followed by the axis component, and the smallest influence on the wall shear stress of the cylinder, i.e., ${\overline{k}}_{{\sigma }_c}$ > ${\overline{k}}_{{\sigma }_a}$ > ${\overline{k}}_{{\sigma }_r}$ > ${\overline{k}}_{{\tau }_c}$ .

With the rapid growth of agricultural trade volumes, the transportation of agricultural products has received widespread attention from society. Aiming at these problems of low transport efficiency and high transport cost in long-distance transport of agricultural products, an energy-saving and environmental-friendly transport mode of agricultural machinery—hydraulic capsule pipelines (HCPs)—was proposed. HCPs effectively solve issues like traffic congestion, energy crises, and atmospheric pollution. Published literature is mainly limited to the capsule speed and the pressure drop characteristics of the fluid within the pipelines. This research was conducted on the following four aspects of HCPs. Firstly, the structure of the carrier was improved and called a ‘piped carriage’. Secondly, a coupled solution between the structural domain of the piped carriage and the fluid domain within the pipelines was numerically investigated by using the commercial CFD software ANSYS Fluent 12.0 based on the bidirectional fluid–structure interaction methods. Thirdly, the effects of guide vane placement angle on hydraulic characteristics of the internal flow field within the horizontal pipelines transporting the piped carriage were extensively evaluated. Finally, based on least-cost principle, an optimization model of HCPs was established. The results indicated that the simulated results were in good agreement with the experimental results, which further demonstrated that it was feasible to adopt the bidirectional fluid–structure interaction methods for solving the hydraulic characteristics of the internal flow field when the piped carriage was moving along the pipelines. This article will provide an abundant theoretical foundation for the rational design of HCPs and its popularization and application.

In the design process for a two-pipe vehicles transportation system, some simple mathematical models are required to quickly calculate the main characteristics of the system. For this purpose, an easy-to-handle mathematical model for the concentric annular gap flow is proposed, and the velocity expression for the concentric annular gap flow is solved using cylindrical coordinates. According to the force characteristics of the two-pipe vehicles, a mathematical model of the two-pipe vehicle motion is established, and the motion and force balance equations of the two-pipe vehicles are deduced. The experimental results are in good agreement with the model results. The factors affecting the two-pipe vehicles movement speed are analyzed, and the standard regression coefficient method in multiple regression analysis is used to determine the influence degree of each factor on the movement speed of the two-pipe vehicles. The research presented in this paper not only enriches the annular gap flow theory, but also provides a theoretical reference for the development of the two-pipe vehicles transportation technology and provides technical support for the realization of relevant industrial applications.

The hydraulic transportation of piped capsules is a new and energy-saving transportation mode, which is especially suitable for the long-distance and high-stability requirements of material transportation. In this paper, the COMSOL Multiphysics software was used to construct a mathematical model of the dynamic characteristics of a piped capsule moving in a straight pipeline, in which the boundary conditions were redeveloped, the inlet velocity distribution function was defined, and the physical experiment was carried out for verification. The dynamic characteristics were analyzed, and through the calculation of the energy consumption, the optimal piped capsule under the research conditions was obtained. The results show that the simulation results and experimental results for the piped capsule’s average moving velocity, axial velocity, and wall shear stress along the cylinder wall were basically consistent, with a maximum error of 14.22%, 2.62%, and 20.13%, respectively. With a decrease in the diameter-to-length ratio of the piped capsule, the axial velocity of the concentric annular gap flow decreased gradually. The area with a large shear stress was mainly concentrated at the front and rear ends of the cylinder wall, especially the rear area of the support feet of the piped capsule. With the increase in the diameter of the piped capsule, the wall shear stress of the capsule increased. Finally, the superior diameter-to-length ratio for the piped capsule under the research conditions was obtained and shown to be ε = 0.4. The research in this paper will provide a theoretical reference for the structural design and dynamic mechanism analysis of the piped capsule.