Search Results (3)

The hydraulic capsule pipeline (HCP) is an eco-friendly and sustainable pipeline transport option. The freight-carrying capsule is driven by hydraulic pipe flow. Fluid drag is generated by the principal dynamic force effect on the capsule, which could influence the capsule’s motion speed. To make the HCP more efficient, a transient model for the hydrodynamic force in an HCP was developed in this study. From a numerical simulation, the coherent vortex structures of fluctuating modes were observed, and the velocity iso-surfaces of the coherent vortex of the wake flow exhibited an annular trend in circumferential connection. Then, the hydrodynamic force was analyzed: the steady component and transient component were resolved, and the general trend in forces in terms of the transient components was that the maximum amplitude of forces reduced with an increase in mode order. Through short-term Fourier transform, the frequency components and their variations in terms of the entire time range could be acquired. The transient model in this study provided a perspective to build the connection between the flow structures and the hydrodynamic force. By the transient model, the transient component of hydrodynamic force can be explained as the fluctuation of coherent vortex structures. Full article

Hydrodynamic forces influence the efficiency and safety of pipeline transport in ocean engineering. A capsule pipeline is an example of pipeline transportation. In this work, a dynamic model is proposed to explain the oscillating motion of a capsule in a hydraulic capsule pipeline (HCP). The main study was conducted using a modal analysis of hydrodynamic forces acting on a capsule, which could be divided into frictional drag and pressure drag forces. The results indicated the presence of independent modes with different contributions to the hydrodynamic forces. Ultimately, the first to fiftieth modes represented 94~97.3% of the hydrodynamic force contributions. These modes had their own frequency ranges and power spectrum density (PSD) functions, and the frictional drag and pressure drag were both found to coincide with the narrow-band characteristics of the lower-order modes. However, the PSD functions of the frictional drag were found to fulfill the wide-band characteristics corresponding to the higher-order modes. Then, coherent structures were extracted. As the mode order increased, the vortices became more fragile and the frequency became higher. This phenomenon coincided with an increase in the frequency of the time coefficient peak, which became larger. This work could provide new perspectives on the hydrodynamic forces of pipeline transport, especially its dynamic analysis of the interaction between a rigid capsule and fluid flow. Full article

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. Full article