Research On Spectral Characteristics Of Wake Bubble Film

During the navigation of the ship,the propeller disturbs the surrounding seawater to form a wake.The wake contains a large amount of ship navigation information,which will show different physical characteristics from the seawater itself.The optical properties of the wake are one of the important components of the physical properties of the wake.The study of the optical properties of the wake has high practical value and is widely used in many fields,such as torpedo homing,ocean exploration and sea surveillance law enforcement.The study of wake bubble film is one of the focuses of wake research.More wake information can be obtained by studying the spectral characteristics of bubble film.In this paper,the spectra of the transmitted light,scattered light and relative irradiance of the wake bubble film are studied and measured,so that we have a deeper understanding of the physical characteristics of the wake.The main research contents include:1.The scattering light characteristics and optical efficiency factors of a single bubble and a bubble film are calculated by Mie scattering theory.The scattered light characteristics of a single bubble are calculated and simulated,including the distribution characteristics of the scattered light intensity of the single bubble and the distribution characteristics of the scattered light phase function.Two different incident light wavelengths of 0.6328μm and 0.532μm are selected,and the scattered light intensity distribution of single bubbles with radii of 0.2～0.9μm and 1～300μm is compared and analyzed.The results show that the scattered light intensity of single bubbles increases with the increase of bubble radius,and there is a tendency of forward concentration.2.The phase function of the scattered light of the bubble film at two incident light wavelengths of 0.6328μm and 0.532μm was simulated and analyzed.The simulation results show that the phase function distribution curve of the scattered light of the bubble film is relatively smooth at both incident light wavelengths.The incident light wavelength has little effect on the distribution of the scattered phase function of the bubble film,and the distribution curve is similar.The intensity of forward scattered light of the bubble film is greater than that of backward scattered light.The optical efficiency factor is studied.The results show that when the wavelength of the incident light is constant and the relative refractive index of the bubble is different from that of fresh water and seawater,the scattering coefficient of the bubble increases with the radius,and the scattering coefficient is closer to 2.The difference is that the oscillation frequency is different.3.The transmission spectrum detection system and relative spectral irradiance detection system were established by using incandescent lamp as the light source in the laboratory environment.The transmission spectrum characteristics and relative spectral irradiance characteristics of the bubble film were studied experimentally,including different measurement heights,different pressures and different bubble film thickness spectral intensity measurements.The experimental results show that with the increase of bubble film thickness,the intensity of transmission spectrum decreases and the relative spectral irradiance decreases.With the increase of air pressure,the intensity of transmission spectrum decreases and the relative spectral irradiance decreases.As the measurement depth increases,the transmission spectrum intensity increases and the relative spectral irradiance increases.4.With He-Ne laser as the light source,the forward and backward scattering light spectrum detection system of wake bubble film is established.The spectral changes of forward scattering light intensity and backward scattering light intensity of wake bubble film with different scattering angles under different pressure conditions are studied respectively.The experimental results show that the forward scattering light intensity and the backward scattering light intensity of the wake bubble increase with the increase of the air pressure,and the bubble number density increases,showing a decreasing trend.When the air pressure is the same,the forward scattering light intensity is greater than the backward scattering light intensity.At the near axis of the optical axis,the scattering angle increases and the scattering light intensity decreases,which is consistent with the simulation results of Mie scattering theory.