Abstract: Abstract: Due to the problems of energy crisis and environmental pollution in the traditional long-distance transportation mode of agricultural products, it has become an inevitable trend to seek a low-carbon and environmentally-friendly transportation mode of agricultural products. In order to further analyze the effect of the fluid-solid interaction on the internal flow field characteristics of the tube-contained raw material pipeline hydraulic transportation, the geometrical model of the tube-contained raw material pipeline hydraulic transportation was established, and the fluid domain within the pipeline and the solid domain of the piped carriage were jointly solved by using a commercial ANSYS Fluent 12.0 software. At the same time, the simulated values obtained by coupling calculation were compared with the experimental values. The unsteady numerical calculation of the fluid domain within the pipeline was based on the Reynolds time-averaged momentum equations and the RNG k-ε turbulent model, and the coupling calculation of the instantaneous speed and displacement of the solid domain for the piped carriage at any time was based on the structural dynamic equations. The tube-contained raw material pipeline hydraulic transportation worked by taking water as transmission medium, sealing agricultural products inside the piped carriage, pushing the piped carriage by using pressurizing devices, and realizing the long distance transport of the piped carriage. This transportation mode had the advantages of low transportation cost, high transportation efficiency and little environmental pollution. The internal flow field characteristics of transporting the piped carriages with a height of 0.1 m and 4 diameter-length ratios of 0.5, 0.6, 0.7 and 0.8 respectively were studied by using the model test. The flow velocity distribution of the typical cross-sections was measured by using the Laser Doppler Anemometry and the photoelectric timing device. The time-average pressure of piezometer tubes was measured by using the standard dynamic pressure collection system and the pressure sensors. The instantaneous speeds and instantaneous displacements of the piped carriages were measured by using the high speed camera. The results showed that the simulated values were in good agreement with the experimental values, which further indicated that it was feasible to adopt the fluid-structure interaction methods to solve the internal flow field characteristics of the tube-contained raw material pipeline hydraulic transportation. As the diameter-length ratio of the piped carriage increased, the affected areas of the axial flow velocity, the radial flow velocity and the pressure gradually increased, the affected areas of the vorticity magnitude gradually decreased, and the affected areas of the circumferential velocity gradually decreased first and then increased near the front end of the piped carriage. The combined effects of both the energy dissipation and the energy conversion caused local low pressure areas to develop near the front end of the piped carriage, but energy conversion caused the downstream pressure of the piped carriage to increase again. The time-average pressure drop coefficients of the piped carriages first decreased and then increased with the increasing of the diameter-length ratio, and the time-average pressure drop coefficient caused by the piped carriage with the diameter-length ratio of 0.7 was the least. During the transport process of the piped carriage along the pipeline, the distributions of the axial velocity, radial velocity, circumferential velocity and vorticity magnitude in the near-wall region of the piped carriage were basically the same, but the pressure distributions showed a gradually decreasing trend. The research in this paper provides an important theoretical reference for the structural design and hydrodynamic mechanism analysis of the piped carriage.