The Research On Ship Wake Bubbles Distribution And Optical Scattering Characteristic

The ship moving and propeller cavitations, which can take air into water and form bubble film which contains a large number of bubbles, Wake motivation bubble film. Wake of the optical properties and application is a new scientific research project at present. That has great significance to the military and civilian industries. For the detection and tracing the underwater object such as aquatic organisms and ships based on optical properties of wakes is a new thought and method, It has farther detected distance, non-interference of electromagnetic noise or ambient noise and higher hit probability. In this thesis, take an analysis on wake bubbles distribution and optical characteristics. This thesis analyzed the wake bubbles distribution and optical characteristics, the emphasis is the light scattering.The first, take a research on wake bubbles distribution, involves the bubbles movement speed and scale of the changes and the density change for research, The critical radius of bubbles is 44.2μm, in the near point of the bubble live the longest time, the radius of between 40 and 50μm bubbles live the longest time, and the density is the biggest.Secondly, the Mie scattering theory applied to the single bubbles light scattering based on the bubbles distribution characteristic. Then, in a model of single bubble take further research on the scattering properties of bubble film, build the model of Monte-Carlo has the further discussion of the character of the bubble film. By the simulated calculation, performed using Monte-Carlo method shows that the bubbles of the light scattering is feasible, for wake light detection provide a more practical method. And studied the distribution of scattering light energy in the far wake field, The forward scattering and back scattering light energy distribution were compared.Finally, Established the light scattering model, the wake bubble light back scattering has been studied much. That shows:(1)With the distance of the ship wave, the effect is not obvious on backscattering and the change of the bubble scattering phase function is smaller. (2) Ship wave bubbles can product obvious scattering signals as a laser incoming, and the signals reduction when the distance adding. The intensity of back scattered light is the biggest in the wake of the lower part of centre district.(3)By experiments indicate:If water is calm, whether in the difference in signal amplitude or in frequency components of the identification, can be used to identify the existence of bubbles, if the water under the large fluctuation, from the received signal spectrum to judge the existence and distribution of bubbles is feasible also.From the studying of theory and experiment, found out the speed of bubbles is linear with the radius is less then lmm, and the intensity of back scattering light is max at 180°.It is feasible that detecting and tracking objects according to the wake light backscattering characteristics.