Experimental Study Of Imaging Methods Of Underwater Microbubbles Through Supercavitation Layer

Supercavitation is a sort of physical phenomenon occurred on the surface of an underwater high-speed sailing vehicle, which can significantly reduces the resistance of vehicle. Detecting bubbles of ship wake by optical methods through supercavitation layer, and studying the differences of density, distribution between bubbles and the surrounding water environment can be used as a sort of ship positioning, and an effective method for high-speed underwater vehicle's guidance.In order to analyze the influence of different experiment conditions on the simulated wake imaging through the supercavitation layer, and select optimal imaging condition, this paper use natural air layer to simulate the supercavitation layer in a lab environment, then using light scattering method to detect and image tiny bubbles with micron diameter through this layer. By changing the experiment conditions, groups of experiment are carried out and the bubble number of image from these groups are obtained after processing the result, the image quality is estimated by bubble numbers which can be detected clearly. With the comparison between experiment groups and theoretical bubble density, the varying pattern with the changing experiment conditions of bubble density is obtained, and the imaging conditions which have bubble density closed to the theoretical value is the best imaging condition.The result shows, when the detection angle is 90 degrees, bubbles have the clearest imaging. The growth of bubble number in imaging is increasing with current and reaching to a certain degree then becoming saturated, and the smaller the diameter of bubble is, the higher sensitivity towards current has. After adding disturbance, it is found that the influence of disturbance on the identifiable bubble number is more obviously when bubble density is bigger.