Abstract
The centrifugal underwater explosion tests and corresponding numerical simulations were carried out to study the laws of shock wave and bubble pulsation. A semiempirical method to determine JWL state equation parameters was given. The influence on numerical results caused by factors such as state equation of water, boundary condition, and mesh size was analyzed by comparing with the centrifugal underwater explosion test results. The results show that the similarity criterion is also suitable in numerical simulation; the shock wave peak pressure calculated by polynomial state equation is smaller than that of shock state equation. However, the maximum bubble radius and the pulsation period calculated by the two equations are almost the same. The maximum bubble radius is mainly affected by the boundary simulating the test model box, and the pulsation period is mainly affected by the artificial cutoff boundary. With the increase of standoff distance of measuring point, the mesh size required for the numerical calculation decreases; the size of the two-dimensional model is recommended to take 1/30 ∼ 1/10 explosion radius. In three-dimensional models, when mesh size is 2 times larger than explosion radius, the bubble motion change in the second pulsation period is not obvious. When mesh size is smaller than 1 time explosive radius, the full period of bubble pulsation can be well simulated, but calculation errors increase slowly and computation time greatly increases, so the three-dimensional mesh size is suggested to take the charge radius. Shock wave peak pressure is basically unaffected by gravity. As the gravity increases, the bubble maximum radius and the first pulsation period both decrease.
Highlights
Underwater explosion plays a vital role in military and civil construction. e load of underwater explosion mainly consists of two parts: shock wave and bubble pulsation, each of which accounts for about 50% of the total energy of explosion [1]
Rm and T are almost unaffected by the state equation of water. e water peak pressures calculated by the polynomial state equation are slightly smaller than that calculated by the shock state equation, so Rm would be slightly larger, but the difference of the state equation did not affect the pulsation period T
According to the test and numerical results, conclusions can be drawn as follows: (1) e shock wave peak pressure calculated by the polynomial state equation is smaller than that calculated by the shock state equation. e di erence in state equation of water has less e ect on the bubble maximum radius and the pulsation period
Summary
Underwater explosion plays a vital role in military and civil construction. e load of underwater explosion mainly consists of two parts: shock wave and bubble pulsation, each of which accounts for about 50% of the total energy of explosion [1]. The centrifugal underwater explosion tests of spherical explosive RDX were introduced, and the corresponding numerical simulations were conducted. On the basis of 1g RDX explosive underwater explosion tests, different finite element models were used to study the influences of various factors, including the state equation of water, the boundary condition, and the mesh size. Combining the numerical results of the optimal numerical model and centrifugal underwater explosion test results, some rules of shock wave and bubble pulsation were summarized. As it can be seen, the calculated variation of the shock wave peak pressure and the bubble radius are almost the same
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