Transmission Characteristics Of Blue-green Laser In Seawater Flow Around The Research

Application of Blue-Green laser technology on high speed sea-based equipment is developed slowly. It is due to the lack of theoretical basis. When the carrier is fast-moving under water, the flow around will affect the optical wave surface, the "valve effect" phenomenon will occurred, such as flickering, drift, mixing and extended. The phenomenon affects the laser transmission paths, that will have an great impact on the laser detection accuracy of the fast-moving carrier. But most current research on static transmission characteristics of underwater laser can not resolve this problem completely, therefore, combining theories of hydrodynamics and Ocean Optics, the blue-green laser characteristics in the dynamic transmission of seawater flow are researched systematically in this paper.Firstly, static transmission characteristics in a blue-green laser in seawater are analyzed, the laser echo power equation under static conditions is derived. In combination with the fluid mechanics theories, such as water bottom boundary layer, turbulence and cavitations, transient concentrations parameters of suspended particulates are derivate, a preliminary model of laser transmission in the dynamic flow is established. Then, with FLUENT software for numerical analysis, the flow field distributions of velocity, pressure, cavitation and solid-liquid two-phase flow are obtained. The relationship between derived distribution of suspended particle concentration and laser distance in seawater is derivate, further dynamic model is refined by using this relationship. Finally, underwater laser test prototype is designed, a flume experiment and water tunnel experiment are carried on, and results indicate that the study program on characteristics of flow around underwater laser is feasible, experimental results and theoretical calculations are matched, the correctness of the theoretical model is verified.This research results can be used to afford the theory basis and design reference for blue-green laser applications on underwater high speed carrier, also a new method for the study of underwater laser is provided by the combination testing methods of computational fluid dynamics and water tunnel experiment.