Analysis Of Ice-induced Noise Characteristics Of Geophysical Exploration Components

As the modernization process advances,terrestrial fossil energy sources are gradually becoming exhausted.In order to seek the sustainable development of human society,the pace of human exploration is gradually moving towards the ocean.Due to the complexity of the marine environment,human knowledge of the ocean is far less than that of other fields.Rich resources are very likely to be contained in the depths of the ocean and have great potential for development.At present,there are abundant flammable ice resources in the ocean,which is estimated to be twice the total amount of carbon in the world’s traditional fossil fuels.The polar regions are covered with ice for many years,which arouses the enthusiasm of human exploration.With the opening up of polar routes and the maturity of shipbuilding technology and detection technology,China has basically possessed the conditions for the exploration of submarine resources in polar regions.In recent years,polar marine geophysical exploration has been gradually put on the agenda.Geophysical exploration ship is an indispensable tool for marine geophysical exploration.It mainly relies on the technology of terrestrial seismic exploration,and uses the source gun array on board to release high-pressure air in seawater as a seismic source for geological exploration.The influence of underwater radiation noise is often ignored in the process of traditional civil ship design and construction.But for the geophysical exploration ship,due to the special nature of its work,excessive underwater radiated noise is likely to interfere with its own detection work,which will directly affect the quality of data collection and reduce the efficiency of the geophysical exploration ship.Therefore,it is necessary to consider the influence of underwater radiated noise on the work of geophysical exploration ships.It is of great engineering significance to carry out prediction of underwater radiated noise of polar geophysical exploration ships.This thesis makes an analysis of the interaction between ice floes and geophysical exploration component;and combines with the methods of experiment and numerical simulation to predict the ice induced noise caused by their collision.Firstly,the experimental analysis of ice induced noise was carried out in the environment of anechoic pool;secondly,the physical model of ice floes and geophysical exploration component was established according to the geometric parameter information of them;thirdly,the underwater radiated noise produced by the collision between them was calculated by the nonlinear finite element method combined with boundary element method;finally,the experimental results were compared with the numerical calculation results to verify the reliability of the calculation results.The specific work of this thesis is as follows:1.According to the characteristics of the working condition of the ship,a reasonable experimental scheme was designed.The ice induced noise experiment was carried out in the anechoic water tank by using an underwater acoustic test system,a number of hydrophones and a charge amplifier.2.According to the information of the geometric parameters of the ice floe in the experiment,the geometric models of the ice floe and geophysical exploration component were established by using the 3D Modeling Software Solidworks.Then the nonlinear finite element method is used,and the professional finite element analysis software ABAQUS was used to calculate the instantaneous structural response of the surface of the geophysical exploration component under the impact of ice floes.The transient displacement response curves of some characteristic points were extracted for analysis,and it is found that the deformation of the structure occurred after the impact,and the deformation was mainly in the direction of impact,and that the response time of the node far away from the impact position lagged behind that of the node near the impact position,because the wave propagation needs a certain time,and that the amplitude of the displacement response of the node near the impact point was significantly larger than that of the node near the impact point,which is due to the attenuation of the wave during propagation.3.Using the boundary element method and applying the acoustic analysis function of LMS Virtual.Lab,the underwater radiation noise characteristics of ice-induced noise were calculated.No reflection boundary conditions were used(regardless of the effect of free liquid surface)The transient displacement response of the structure surface calculated by the finite element method was used as the acoustic boundary condition,and the radiation noise characteristics without considering the free liquid surface were calculated.And compared the simulation calculation results with the experimental results,and selected the sound pressure(dB)of the characteristic points at the same position for comparison,The study found that the trend of the sound pressure curve of the two was basically the same,and the error of the effective value of the sound pressure was within 10%.It can be seen that the simulation calculation results were in good agreement with the experimental results,which proved the reliability of the simulation results.4.Given the influence of sea level on underwater radiated noise,the boundary element method was also adopted.An antisymmetric plane with zero sound pressure in calculation was used to simulate the free liquid surface,and the underwater radiation noise characteristics considering ice-induced noise under sea level were obtained.In order to view the distribution of the sound pressure of underwater radiated noise in the horizontal direction,a grid of field points was established in the plane of the longitudinal section of the geophysical exploration component,and the variation law of the sound pressure of the field point with the distance was analyzed.