Dynamic Response Analysis Of Structure Under Underwater Explosion

The underwater explosion needs considering five parts:shock wave, cavitations and bubble, jet, fluid-solid coupling phenomenon, the dynamic response of structure. In this paper, the flow field of the bubble pulsation was solved by using the theory analysis and numerical simulation method under near the underwater explosion. The response of the plate under the bubble pulsation pressure effect was analyzed. Connection the underwater acoustic energy and explosion shock wave, by using the fluid-solid coupling method the failure of cylindrical shell and the vibration response of cylinder under the far fielded directional shock wave was researched. For the underwater acoustic energy technology attacking the near ship target provides basis.The bubble produced by near underwater explosion was analyzed. According to the one dimensional incompressible fluid unsteady motion theory, considering addition the work by the virtual force, the existing law equation of bubble pulsation underwater explosion was improved. Comparison analysis the calculation results with the experimental values, considering the addition of the virtual force, the radius, period and velocity of the calculation bubble pulsations by the theory formula were more anatomists with the practical condition. Further improving the law equation of bubble pulsation pressure distribution, the addition effect of the bubble energy, the results were more according with the practical condition than previous analysis.Under the near bubble pulsation, the bubble pulsation load was treatment for spherical wave. Then the clamped circular plate was affected by it. By the Ritz equation the deflection formula of the circular plate was calculated. The income data were fitted a unified formula. Based on the deflection change graph, the center of circular plate was most easily failure. The boundary of circular plate also possibly was damaged under the condition of the thin plate.According to the features between the underwater acoustic energy technology and explosion, the acoustical parameters were converted into the form of explosion shock wave pressure. The strength analysis of cylindrical shell was calculated under the effect of the shock wave. According to the feature of the far field shock wave, it was assumed plane wave to directly apply on a little layer water surface nearby the shell. Using the fluid-solid coupling analysis method of LS-DYNA, the strength of the cylindrical shell was simulation calculated under effect of the underwater directional acoustic energy at 30m. Over 280db sound source grade of the underwater directional shock wave could be certain failure to the cylindrical shell at 30m.The dynamic response of cylinder was simulated under the effect of underwater directional acoustic energy at 100m. When the cylinder was affected by the large energy shock wave pressure, the response of acceleration was rapidly reached the peak which was large and the waveform was steep. However, due to the cylinder coupling with water the vibration energy was quickly dissipated. When the acceleration reached 30g, the internal components may be failure. If according to this standard test the failure situation was caused by the vibration of cylinder. When the sound source grade≥280dB, the internal components maybe could be damaged because of the vibration.The theory and numerical basis were provided by the contents in this paper for the underwater directional acoustic energy technology attacking the near ship target.