Light Scattering And Shape Evolution Of Bubbles In Different Liquids

The research of wake bubble has become one of hot spots of the defense and military in 21st Century. The new technology based on the detection of the wake bubble, which can not only be identified in the low-altitude airborne radar remote sensing, but can be detected by space-borne Interferometric Synthetic Aperture Radar (IFSAR) in deep space, besides, the underwater torpedo equipped with a wake bubbles guidance system also can be tracked to identify the ship wake thus targets, has great military value in future.The research of wake bubble can be divided into two direction:the first, reflected in the macroscopic, researches the sea surface characteristics of ship wake, such as the geometric shape and its evolution over time, the relationships between the absorption and reflection spectral of the sea surface with the surrounding temperature signal, the system of remote sensing image of ship wake and target recognition, and so on. The second reflected in the microcosmic, researches the physical characteristics of bubbles in localized space, as the shape evolution, scale distribution, number density distribution, survival time, the rising speed, the optical absorption and scattering of bubbles in the wake region. These two studies, although with its own research methods, means of detection, and application advantages, are closely linked to each other. As the theoretical and experimental research of bubbles can provide a theoretical basis and experimental evidence for ship wake, the research of ship wake can test and promote the bubble research from a larger spatial extent and the practical application.Two aspects of the research work, which through theoretical calculations and experimental measurements with the medium of fresh water and saline water, has been done in this paper. On the one hand, the light scattering of bubbles in different liquids was researched, as well as the forward scattering of laser by bubbles in saline is analyzed. On the other hand, the shape evolution of rising bubbles was qualitative analyzed through photographing the dynamic image of bubble films in water.Theoretically, based on the Mie scattering theory, the optical scattering efficiency, scattering phase function and intensity distribution of signal bubble, and the phase function of three different scale distributions bubble group in fresh and saline water were calculated using MATLAB firstly. Then the relative percentage of forward scattering of laser by bubbles in saline is analyzed compared with bubbles in fresh water.And based on the experimental measurements,the Difference-value Method which can be used for detecting bubble film in liquid through calculating the change in illumination and the relative percentage of light scattering with and without bubble film is proposed.Theoretical calculation result shows that forward light scattering by the same scale distribution bubble group in saline increases up to 14 percent and decreases with the increasing scattering angle compared with fresh water. Forward light scattering in saline without bubble increases somewhat than fresh water,the mean relative forward scattering (MRFS)increases about 10 percent for the same liquid with the pressure increasing. However,MRFS increases about 5 percent compared with fresh water at the same pressure.