Research On The Physical Parameters Of Ice Layer And The Acoustic Inversion Method Of Its Profile

The Arctic is covered by ice all the year round.Polar ice has an important impact on the global climate.To accurately understand the physical parameters of polar ice,especially temperature,salinity,density and its profile changes,is to fully understand the dynamic changes of polar ice.Important parameters.In addition,when sailing in the new Arctic Channel,polar sea ice is the main environmental factor to be considered for ship navigability.The load response of sea ice to the hull is related to ice thickness and mechanical parameters,and its mechanical properties are ice layers.Function of temperature,salinity and density.It can be seen that whether it is to predict the impact of Arctic sea ice on the global climate or to ensure the safety of ships in the polar regions,it is of great practical significance to obtain and fully understand the changes in temperature,salinity,density and profile of polar ice..For the method of obtaining the ice layer temperature,salinity and density,the traditional insitu borehole sampling method is usually used for measurement.The disadvantages of this method are that it is time-consuming,labor-intensive,and inefficient.Parameter information has caused great difficulties in conducting efficient and accurate scientific investigations in the Arctic.Therefore,there is an urgent need for a safer,faster and larger-scale method for obtaining physical parameters of ice layer.In response to this problem,this article analyzes the characteristics of the Arctic ice layer temperature,salinity,and density,establishes a function model of the sound velocity with respect to the ice layer temperature,salinity,and density,and proposes an acoustic inversion method for the physical parameters of the ice layer.And the parametric array ice measurement technology is used to better obtain the physical parameters of ice in a large area.Focusing on the purpose of the study,this article first studied the characteristics of the three physical parameters of natural ice temperature,salinity,and density based on the measured data from the 3rd,4th,5th,6th,7th,and 9th Arctic scientific expeditions,and analyzed its profile changes.Law,and fitted the binary function of density in ice with respect to temperature and salinity.Then,taking the porosity in ice as an intermediate quantity,the sound velocity in ice as a function of temperature,density,and salinity was used to establish a model of sound velocity in ice.Based on this,an improved particle swarm optimization(SA-PSO)algorithm based on simulated annealing is used as the optimization algorithm in the inversion method,and an ice layer physical parameter profile inversion method based on the sound velocity model in ice is proposed.In order to improve the ability of measuring ice,a method for measuring the average sound velocity in ice based on an acoustic parameter array was studied.Take full advantage of the low-frequency,small size,narrow directivity,and no sidelobes of parametric arrays,that is,low-frequency low-frequency sound waves can penetrate thicker ice layers,and small-sized transducers can reduce the impact on the platform(such as AUV).The requirement of size limitation,narrow directivity can improve the measurement accuracy,and the sidelobe beam can eliminate the problem of false echoes.Because the parametric array is a complex non-linear self-demodulation process of large amplitude waves in water,the modulation technology of parametric array transmission signals is the key technology in the ice measurement of the parametric array.This article is based on the theory of the parametric array "Berktay far-field solution".The double integral quadratic modulation algorithm and recursive filtering parametric modulation algorithm are studied.Finally,a pool experiment and an external field test were carried out to verify the feasibility and effectiveness of the acoustic inversion method for the physical parameter profile of the ice layer.The research results in this article provide an effective means to quickly and widely obtain information about the physical parameters of the Arctic ice layer,provide potential new technical support for polar navigation and resource development,and contribute technical power to the country's "polar strategy."...