Results of modeling the dependence of the height of flexural-gravity waves in a floating plate with a sealed edge on the inclination of the bottom of the reservoir

На основании проведенных автором экспериментов по разрушению льда амфибийными судами на воздушной подушке (СВП) резонансным методом при их движении в сторону берега, их крупномасштабных моделей в полевых условиях, а также известных случаев разрушения ледяного покрова движущимися в сторону берега транспортными средствами показана возможность существенного увеличения толщины льда, разрушаемого у его береговой кромки. Приведены данные экспериментов, выполненных в опытовом бассейне на моделирующих ледяной покров упругих пленках, подтверждающие эти возможности. В работе представлены результаты моделирования зависимости высоты изгибно-гравитационных волн (ИГВ), возбуждаемых в плавающей пластине движущейся в направлении ее заделанной кромки нагрузкой, от угла наклона дна бассейна. Также приведены рекомендации по использованию наклонности дна для повышения эффективности разрушения ледяного покрова (увеличения толщины разрушаемого льда) путем возбуждения резонансных ИГВ. На основании выполненных экспериментов показано, что приближение к берегу ИГВ, возбуждаемых СВП с последующим их выходом на него, может значительно увеличить толщину разрушаемого льда за счет отрыва от берега его кромки. Отмечена возможность увеличения ледоразрушающей способности ИГВ благодаря последующим проходам судна вдоль нее из-за роста деформаций ослабленного таким образом льда, т.е повышения ледоразрушающей способности СВП. Based on the experiments conducted by the author on ice destruction by amphibious hovercraft using the resonant method when they move towards the shore, their large-scale models in the field, as well as known cases of ice cover destruction by vehicles moving towards the shore, the possibility of a significant increase in the thickness of ice destroyed at its coastal edge is shown. The data of experiments performed in the experimental pool on elastic films modeling the ice cover are presented, confirming these possibilities. The paper presents the results of modeling the dependence of the height of Flexural-gravitational waves excited in a floating plate by a load moving in the direction of its embedded edge on the angle of inclination of the pool bottom. Recommendations are also given for using the bottom slope to increase the efficiency of ice cover destruction (increasing the thickness of the destroyed ice) by exciting resonant Flexural-gravitational waves. Based on the performed experiments, it is shown that the approach to the shore of Flexural-gravitational waves excited by hovercraft with their subsequent exit to it can significantly increase the thickness of the destroyed ice due to the separation of its edge from the shore. The possibility of increasing laboratree the ability of the Flexural-gravitational waves during the next passages of the ship along it due to the growth of deformations weakened the ice.

Bragg Scattering of Surface Gravity Waves Due to Multiple Bottom Undulations and a Semi-Infinite Floating Flexible Structure

Surface gravity wave interaction with a semi-infinite floating elastic plate in the presence of multiple undulations has been studied under the assumption of linearized water wave theory and small amplitude structural response. The elastic plate is modeled using the Euler-Bernoulli beam equation, whilst the multiple undulations are categorized as an array of submerged trenches or breakwaters. The numerical solution obtained in finite water depth using the boundary element method is validated with the semi-analytic solution obtained under shallow water approximation. Bragg resonance occurs due to the scattering of surface waves by an array of trenches or breakwaters irrespective of the presence of the floating semi-infinite plate. The zero-minima in wave reflection occur when the width of the trench and breakwater is an integer multiple of 0.6 and 0.35 times wavelength, respectively, as the number of trenches or breakwaters increases. In contrast to trenches and breakwaters in isolation, non-zero minima in wave reflection occur in the presence of a semi-infinite plate. Moreover, the number of complete cycles in trenches is less than the number of complete cycles in breakwaters, irrespective of the presence of the floating structure. The frequency of occurrence of zero minimum in wave reflection is reduced in the presence of the semi-infinite plate, and wave reflection increases with an increase in rigidity of the floating plate. Time-dependent simulation of free surface displacement and plate deflection due to multiple undulations of seabed in the presence of the semi-infinite floating plate is demonstrated in different cases.

Analysis of hidden safety hazards and treatment suggestions when the floating roof of oil storage tanks falls to the bottom

In the actual production and operation of enterprises, it is sometimes inevitable that the floating roof will fall to the bottom. This paper calculates the explosion limit of the mixture of oil gas under the floating roof, and confirms that the concentration of oil gas will be within the explosion limit under certain circumstances. Through the monitoring and analysis of the oil-gas mixing space below the floating roof, corresponding control measures are proposed to deal with the potential safety hazards of the floating plate falling to the bottom.

Mechanism of Drag Reduction in Floating Plate of Paddy Field Based on CFD

In order to study drag reduction mechanism in mud parts’ operation of surface machine tools for paddy field, this paper takes floating plate, the main working part of laminating mechanism, as the research object and systematically analyzes the mechanism of action of elevation angle, curved angle, penetrating angle, and local microstructure of floating plate on working resistance and local fluid flow characteristics of the laminating structure based on VOF model in Fluent. Using ship mechanics theory and fluid lubrication theory, the drag reduction mechanism under different structural parameters of the floating plate is analyzed. The results show that, compared with the ordinary floating plate, the pressure difference resistance can be reduced by increasing the elevation angle by 60°, curved angle by 20°, and mud separation angle by 20°. The increase of the concave nonsmooth bottom surface structure can reduce viscous frictional resistance, and the total working resistance after structural optimization is comparatively reduced by 48.3%, with lowered hilling height in the forward direction and improved lubrication condition of the bottom surface, forming liquid lubrication effect. This study can provide theoretical references for the optimization design of muddy soil mud parts, mud-machine interaction research, and the development of paddy field laminating mechanism.

Scour Protection Effects of a Geotextile Mattress with Floating Plate on a Pipeline

Underwater pipelines are vital to the oil industry. Extending the service life of these pipelines is a key issue in improving the sustainability of oil transportation. A geotextile mattress with floating plate (GMFP) is a novel and sustainable countermeasure for scour and erosion control and is herein introduced to protect a partially buried pipeline from local scour in steady currents. A series of experiments was designed to verify the protection capabilities of the GMFP and investigate its parametric effects on protection. The average seepage hydraulic gradient under the pipeline was adopted to depict the protection effects of the GMFP, and was calculated with the pore pressure readings under the pipeline. The test results show that the GMFP is capable of protecting a pipeline from the onset of local scour in a unidirectional current. The average seepage hydraulic gradient below the pipeline decreases remarkably after a GMFP is installed. The average hydraulic gradient shows a descending trend with increased sloping angle α when 0.64 < sinα < 0.77. The hydraulic gradient hits a nadir at sinα = 0.77 and climbs with the increasing sloping angle when sinα > 0.82. The hydraulic gradient ascends when the bottom opening ratio δ increases from 0.167 to 0.231, due to the decreased intensity of the bottom vortex. The hydraulic gradient drops with a rising plate height, except for a fluctuation at Hp = 0.12 m. An approximate negative correlation is found between the obstruction height of the floating plate and the average hydraulic gradient under the pipeline. This could be partially attributed to the extension and amplification of the bottom vortex on the leeside of the pipeline due to the increased plate obstruction height.