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BackgroundThe flow induced vibration of spiral tube bundle widely exists engineering practice. The traditional fluid medium is water and air, whilst lead bismuth fluid has gradually become a new heat exchange medium in recent years.PurposeThis study aims to analyze the flow induced vibration of single row tube bundle in cross lead bismuth flow.MethodsThe computational fluid dynamics (CFD) analysis code FLUENT and the finite element analysis code ANSYS were used to simulate the flow induced vibration of a single row spiral tube bundle. The flow field profile and structural response at different times were analyzed respectively, and the corresponding relationship between the flow field change and structural vibration was explored. The physical insight into the flow induced vibration of the tube bundle was provided.Results & ConclusionsSimulation results show that the vortex shedding occurs in the single row tube bundle in the cross lead bismuth, and the frequency of vortex shedding increases with the increase of the flow velocity. Due to the interference of vortex shedding between the pipes, the vibration frequency of the middle pipe is mainly two times of vortex shedding frequency, while the vibration response of the pipes on both sides is dominated by the vortex shedding frequency, accompanied by a small frequency doubling. With the increase of the flow velocity, the influence of the interference between pipelines on the frequency doubling vibration response of pipeline vibration is gradually weakened. When the inlet velocity exceeds a certain value, the amplitude of the pipe increases suddenly, causing fluid-elastic instability of the pipelines.

The local-resonance bandgap performance of piezoelectric metastructures could be deteriorated by the inherent resistance existing in the piezoelectric patches and the inductors of shunting circuits. In this article, we propose to use negative-resistance circuits to cancel the inherent electrical resistance and therefore enhance vibration reduction performance in the bandgap. The physical model of the piezoelectric metastructure with negative-resistance shunting circuits is firstly illustrated, followed by analyzing its wave dispersion relations and frequency response functions. The enhanced bandgap performance of the piezoelectric metastructure facilitated by negative-resistance circuits is verified with the analytical results. Last, an experimental setup of the piezoelectric metastructure is built. The experimental results demonstrate that the vibration suppression performance in the bandgap is significantly increased by using negative-resistance circuits, and a higher value of negative resistance could lead to larger vibration reduction. Overall, the results of this article provide a novel means to enhance the local-resonance bandgap performance of piezoelectric metastructures. [ABSTRACT FROM AUTHOR]

A variational method is proposed to study the free vibration of joined cylindrical-conical shells (JCCSs) subjected to classical and non-classical boundary conditions. A JCCS is divided into its components (i.e., conical and cylindrical shells) at the cone-cylinder junction. The interface continuity and geometric boundary conditions are approximately enforced by means of a modified variational principle and least-squares weighted residual method. No constraints need to be imposed a priori in the admissible displacement functions for each shell component. Reissner-Naghdi's thin shell theory is used to formulate the theoretical model. Double mixed series, i.e. the Fourier series and Chebyshev orthogonal polynomials, are adopted as admissible displacement functions for each shell component. To test the convergence, efficiency and accuracy of the present method, free vibrations of JCCSs are examined under various combinations of edge support conditions. The results obtained in this study are found to be in a good agreement with previously published results where possible, and those from the finite element program ANSYS. The effects of elastic foundation stiffness and semi-vertex angle on frequency characteristics of the JCCSs are also discussed. [ABSTRACT FROM AUTHOR]