Experimental study on cavitation effect of claw apparatus of bionic snapping-shrimp under submerged condition

Abstract

Traditional underwater acoustic jammers are usually large and complex, which causes frogman troops to be exposed in communication-jamming missions. In this paper, a new claw apparatus of bionic snapping shrimp was designed and manufactured based on the characteristics of cavitation noise generated by the high-speed closure of the claw of snapping shrimp. The cavitation erosion effect and cavitation noise of the apparatus were investigated experimentally. The results of the study are as follows: A new bionic apparatus was designed and manufactured on the basis of simplifying the structure of the claw of snapping shrimp. The cavitation erosion effect of the bionic apparatus at different target distances was obtained by using the 50 μm aluminum foil as the target. By analyzing the cavitation image of aluminum foil, it is found that the cavitation effect increases first and then decreases with the increase of target distance. And the target distance corresponding to the maximum cavitation diameter is 43 mm. The binarization processing was carried out on cavitation erosion images. By calculating its cavitation erosion area, it was found that the largest area appeared at 41 mm and the corresponding cavitation erosion area reached 6379.1px. Then the cavitation noise generated by the bionic apparatus was measured with hydrophones at different rotation angles of dactyl and target distances. And the cavitation noise was detected successfully by importing wavelet analysis into noise analysis and processing. Based on the three-layer wavelet decomposition, the energy value of the wavelet packet was calculated, and the PSD analysis based on the hydrophone sensitivity modification was carried out. Finally, the frequency distribution of the cavitation noise signal and the sound pressure level was studied.