As the demand for ocean exploration grows, nuclear reactors utilizing natural circulation for power generation have become a significant propulsion force for long-term operations. However, the coolant within the react...
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As the demand for ocean exploration grows, nuclear reactors utilizing natural circulation for power generation have become a significant propulsion force for long-term operations. However, the coolant within the reactor system is influenced by ocean conditions, characterized by passive flow fluctuations. In this study, a onedimensional (1d)/three-dimensional (3d) coupling analysis method is developed and applied to investigate the impact of heaving conditions on the flow and heat transfer performance of natural circulation with a narrow rectangular channel. The flow and heat transfer characteristics within the narrow rectangular channel, which represents the reactor core, are analyzed in detail using a three-dimensional approach, while the overall natural circulation performance of the system is assessed using a one-dimensional method. Validation is conducted based on pulsating flow experiments and natural circulation experiments. Subsequently, detailed thermal-hydraulic parameters for both the rectangular channel and the natural circulation system are obtained. The results indicate that flow fluctuations caused by the heaving conditions significantly influence the transient performance of both the rectangular channel and the entire natural circulation system. However, the time-averaged flow resistance and heat transfer capability remain unaffected by the heaving conditions. An increase in the heaving period results in a decrease in flow fluctuations within the natural circulation system, and the phase delay between heaving displacement and mass flow flux also diminishes. Conversely, as the heaving amplitude increases, flow fluctuations rise, but this has no effect on the phase delay. due to the ring effect introduced by the heaving motion, the difference between the main flow zone and the wall zone dominates the transient thermal-hydraulic performance in the narrow rectangular channel. Additionally, the heaving motion does not significantly influence the cycle-aver
The objective of this paper is to analyze a coupled problem that describes the propagation of the electric wave in the heart. The problem comprises coupled partial differential equations posed on a three-dimensional d...
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The objective of this paper is to analyze a coupled problem that describes the propagation of the electric wave in the heart. The problem comprises coupled partial differential equations posed on a three-dimensional domain representing the heart and on a one-dimensional tree representing the Purkinje network. Each system of PdEs is itself coupled to ordinary differential equations that describe the electrical activity at the cellular level. We establish the existence of a unique solution, utilizing a fixed-point approach with a judicious and non-conventional choice of functional spaces and contraction.
Pipelines in Nuclear Power Plants (NPPs) work under high pressure and temperature which may cause a guillotine rupture on the highly pressurized pipe during a sudden fracture due to a failure of any working component....
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Pipelines in Nuclear Power Plants (NPPs) work under high pressure and temperature which may cause a guillotine rupture on the highly pressurized pipe during a sudden fracture due to a failure of any working component. Owing to the serious safety concerns resulting from such failures, it becomes important to understand the behaviour of these pipe structures under dynamic loading, particularly, the pipe whipping effect. Therefore, this research study deals with understanding the structural response of pipe whip with a computationally efficient Finite Element (FE) model. The complete three-dimensional (3d) FE model is modified and coupled with a one-dimensional (1d) FE model (coupled1d/3d FE model) and solved under the exact transient conditions, and compared with the complete 3d FE model. The computational time of the complete 3d approach was reduced to about 10 times using the coupled1d/3d model without compromising on the accuracy of the numerical results. Furthermore, the numerical results were found to be in close agreement with the referenced experimental data. This research provides justifiable results from the FE models where the dynamic behaviour of high-pressure pipes under transient conditions can be simulated by using the proposed coupled1d/3d modelling approach.
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