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The leakage mechanism of the clamp connector for submarine pipeline is investigated. The contact seal of a clamp connector is regarded as a half-cylinder squeezing a plane. Moreover, mean stress of the contact region is used to calculate the permeability, based on an observation length-dependent mechanic model and a new fractal porous media model. The analysis yields insight into the effects of surface fractal parameters on the permeability, when mean stress rises within the yield limit. Compared with experiment results, the prediction of this model shows well consistency in the trend.

Wave energy is acknowledged as one of the most promising renewable energy sources, effectively developing wave energy conversion technologies might contribute to solving the power shortage dilemma. However, the optimum performance frequency range of current wave energy capture devices does not match the low-frequency ocean kinetic energy. Here, a triboelectric nanogenerator based on liquid mercury (M-TENG) is presented for low-cost and high-power harvesting. The start-up performance of the M-TENG unit is analyzed at low operating frequencies, and discuss the effect of kinematic inputs, structural parameters and materials aspects on output performance. Meanwhile, the sloshing characteristics of mercury in a rectangular unit were calculated by the SST k-ω model, deriving the matching law between mercury volume and electrical output. Furthermore, 18-unit integrated M-TENG produce a peak power output of 4.57 mW, the mercury with its unique physical properties generates higher transferred charge density up to 35.84 mC/m3, sufficient to light 270 commercial LEDs at 1.00 Hz. The relatively high volumetric power density provides a realistic self-supply technological solution for renewable energy harvesting and guarantees the widespread use of milliwatt power equipment in the marine industry.

The wave energy, as a clean and non-pollution renewable energy sources, has become a hot research topic at home and abroad and is likely to become a new industry in the future. In this article, to effectively extract and maximize the energy from ocean waves, a vertical axisymmetric wave energy converter (WEC) was presented according to investigating of the advantages and disadvantages of the current WEC. The linear and quadratic equations in frequency-domain for the reactive controlled single-point converter property under regular waves condition are proposed for an efficient power take-off (PTO). A method of damping coefficients, theoretical added mass and exciting force are calculated with the analytical method which is in use of the series expansion of eigen functions. The loads of optimal reactive and resistive, the amplitudes of corresponding oscillation, and the width ratios of energy capture are determined approximately and discussed in numerical results.

An array of floating point-absorbing wave energy converters (WECs) is usually employed for extracting efficiently ocean wave energy. For deep water environment, it is more feasible and convenient to connect the absorbers array with a floating body, such as a semi-submersible bottom-moored disk, whose function is to act as the virtual seabed. In the present work, an array of identical floating symmetrically distributed cylinders in a coaxial moored disk as a wave energy device is proposed The power take-off (PTO) system in the wave energy device is assumed to be composed of a linear/nonlinear damper activated by the buoys heaving motion. Hydrodynamic analysis of the examined floating system is implemented in frequency domain. Hydrodynamic interferences between the oscillating bodies are accounted for in the corresponding coupled equations. The array layouts under the constraint of the disk, incidence wave directions, separating distance between the absorbers and the PTO damping are considered to optimize this kind of WECs. Numerical results with regular waves are presented and discussed for the axisymmetric system utilizing heave mode with these interaction factors, in terms of a specific numbers of cylinders and expected power production.