Simulation And Measurement Of Multiple Scattering Of Bubbles In Underwater Wakes

Ship wake is one of the important information in ship traveling.The analysis of it can get many data about ship traveling,which has been paid more and more attention in recent years.There are three parts in the wake of a ship,including bubbles,turbulence and impurities.This paper focuses on the optical scattering properties of the bubbles in the wake of the ship.In this paper,the Mie scattering characteristics of a single bubble are studied by numerical simulation,and the intensity distribution of the single bubble scattering at different angles is obtained.In the experiment,a new scheme was adopted to measure the diameter of the loaded bubbles.A single bubble scattering experiment is carried out by this device,the results of simulation and experiment are analyzed.In the numerical simulation of multi bubbles,firstly,the advantages and disadvantages of Monte Carlo algorithm are analyzed.Its inherent defects in multi bubble simulation are pointed out.The frequency tracing algorithm is proposed.Its key idea is to calculate the path of the bubble in each scattering.By using the frequency tracing algorithm,the Mie scattering intensity distribution of the multiple scattering by the bubble group(the number of times the beam passes through the Mie scattering)is analyzed.Subsequently,we use the results of Mie scattering by a single bubble to explain the result of the multiple scattering by the bubble group.Then,we prove that the Mie scattering of the bubble group has depolarization effect by using the frequency tracking method.The polarization’s degree of the light after scattering by multi bubbles is calculated.The tendency and principle of polarization change are analyzed,and the degree’s expected value of polarization after more scattering is given.Finally,the scattering of bubbles is experimentally verified.The intensity distribution of the wake bubble group’s forward Mie scattering is studied by using a slide device and a flume device to carry bubbles.The experimental results and simulation results are compared.The depolarization effect of Mie scattering has been proved by using the beam less and the beam expanding laser as the light source respectively.The degree of polarization after Mie scattering is calculated by experiment.Then the experimental results are compared with the simulation results.