Study On Modeling Of Sound Velocity In The Ice And Ice Thickness Detection Technology

The Arctic area has abundant fishery,mineral and channel resources,and the ice in the Arctic is also the natural bunker of the strategic nuclear-powered submarine.So there are enormous and potential development space in the shipping channel,resource exploration,military and scientific research in the Arctic area.But the grounded or floating polar ice brings a huge threat for the ship navigation,working on the icebergs and submarine floating.The ice thickness detection and prediction is a key link in the process of submarine safety floating in the polar waters.In order to ensure the safety of a series of development activities in the Arctic area,a reliable ice thickness measurement technology is needed urgently.In this background,an ice thickness detection technology based on acoustic method is studied to provide technical support for the national polar strategy.Based on the research target,firstly,the characteristics of sound velocity in the ice are studied and a model of sound velocity in the ice is established in this paper.The function of sound velocity in the ice and the porosity is derived.And based on the derived function,a lot of experiments were carried out.The experimental data are regression-fitted using Least Square method to get an empirical formula for sound velocity about the porosity.And the empirical formula has been verified through experiments.Secondly,the ice thickness detection technology on the basis of Upward Looking Sonar is studied in this paper.Two kinds of time delay detector that include the alpha comparator dealing with CW signal and the correlation coefficient matched filter dealing with LFM signal is studied.The computer simulation and experiment are conducted.The results prove that the precision of these two time delay detection methods is high and time delay of the echoes from the ice-water interface and the ice-air interface can be detected effectively.In order to improve the accuracy of ice thickness detection,the sound ray correction technology which use the moving of mobile platform to correct the propagation ray.Considering the problem that the sound velocity is unknown,the sound velocity estimation technology is studied,and a sound velocity rapid prediction model that is suitable for engineering application is established.In the end,the tank ice thickness measurement experiment and the Songhua River ice thickness measurement experiment are conducted.The results of experiments indicate that the ice thickness detection technology can get a large number of reliable ice thickness measurement data with high precision.The empirical formula of sound velocity in the ice and the ice thickness detection technology on the basis of Upward Looking Sonar that are studied in the paper can provide some reference value for the equipment development of polar ice measurement.And the ice thickness measurement technology has great significance for polar development,the safety of offshore platform and gas exploration and operation above the ice in high latitudes of our north China.