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[Objectives] As an important component of the connecting circuit,the reed contact switch has been widely used in the electrical system of the naval ship. The switch is very sensitive to underwater non-contact explosion impact,and thus once damaged,it may lead to the failure of the electrical system. This paper studies the impact resistance of the reed contact switch in order to determine its critical working conditions.[Methods] To this end,this paper employs the finite element method to simulate the impact process,and analyzes the response characteristics of different frequency bands based on the critical acceleration amplitude of the corresponding band derived from the triangular wave impact load of certain band applied to the switch model.[Results] The results show that the switch contact will be separated once the shock spectrum of the excitation force at a fixed point exceeds the allowable value. Thus,the preload should be increased to improve the impact resistance of the switch.[Conclusions] This study provides the basis for the research on the damage modes and the protection of the electrical switches of naval ships.

[Objectives] As an important component connecting the equipment and structure of a submarine, the shock resistance of the base structure has an important impact on the ship's survivability. It is simple and efficient to calculate the shock resistance of the base and equipment using the equivalent static load method, but it has higher accuracy only if the lower order response is the main failure mode. [Methods] In this paper, the relative error of structural stress between the static G method and Dynamic Design Analysis Method(DDAM) design spectrum method is studied by taking the air bottle-base structure as the object of analysis. When the low order modal mass of the base structure is occupied in different proportions, the relative error and stress distribution between the equivalent static load and DDAM design spectrum method is analyzed. Taking the actual shock environment of the submarine structure as the input load, the equivalent relation between the DDAM design spectrum and actual shock environment is analyzed. [Results] Precise results are obtained by using the static G method when the single modal mass of the ship's equipment structure is relatively large. For equipment constructed on the deck of a submarine, the shock load stipulated in GJB 1060 is basically equivalent to the shock environment when the shock factor is 0.7 and the explosion source is on the same cross-section as the base structure. [Conclusions] This research can provide useful references when selecting shock resistance evaluation methods for shipboard equipment.

As an installation and protection device for electrical and electronic components, a shipboard cabinet is a typical multiplate structure. In order to study the impact environment distribution laws of such structures, impact testing was carried out on a shipboard cabinet under four working conditions in this paper. In addition, the impact response characteristics of such a multiplate structure were determined by numerical simulation and theoretical analysis. The impact environments of some pivotal points in cabinet were measured and some laws of dynamic response were found. The impact environment of central position was more severe on a single plate because of the first vibration modal. For different plates, the responses were usually similar at low-frequency band and a little different at high-frequency band. The theoretical analysis of the single degree of freedom oscillator was carried out, and the sensitivity of the response to the different characteristic frequencies was discussed based on the shock spectrum theory. A new method of calculating the response at a special frequency was proposed and verified. [ABSTRACT FROM AUTHOR]

A numerical study has been conducted to analyze boundary effects, including different inlet boundary conditions and different inlet section lengths (distances from the inlet boundary to the heated section), on flow dynamics in transient supercritical-pressure heat transfer of n -decane in a circular tube. As the inlet boundary condition changes from a constant flow velocity to a constant stagnation pressure, the pressure oscillation frequency is nearly doubled, and the thermoacoustic wave is in the first longitudinal mode. The frequency of mass flow rate oscillation is essentially the same as that of the pressure wave. Different inlet boundary conditions exert no effect on the pressure wave amplitude but make strong influence on the amplitude of mass flow rate oscillation at the outlet of the heated section. As the inlet insulation section length increases under a constant inlet stagnation pressure, frequencies of both pressure and mass flow rate oscillations proportionally decrease, and the thermoacoustic waves remain in the first longitudinal mode. Different inlet section lengths appear to make only minor effect on the amplitudes of both pressure and mass flow rate oscillations at the outlet of the heated section, and the maximum amplitude in each wave is around 10% of its steady-state value. [ABSTRACT FROM AUTHOR]

To evaluate the potential benefits of kerosene-based nanofluids as coolants for regenerative cooling system, a detailed numerical study of the turbulent heat transfer of copper/n-decane nanofluid flowing inside a miniature cooling tube at supercritical pressures has been conducted. Numerical results reveal that copper nanoparticles can significantly improve heat transfer performance in the entire cooling tube. This can be explained by the fundamental mechanism that within the near-wall turbulent flow region, the reduction of nanofluid kinematic viscosity leads to increased turbulent thermal conductivity and consequently causes heat transfer enhancement. Moreover, heat transfer deterioration phenomenon is delayed or weakened by nanoparticles, and the overall heat transfer performance of the base fluid has been improved. Results indicate potential advantages of kerosene nanofluids as coolants for regenerative engine cooling applications. [ABSTRACT FROM AUTHOR]