Calibration of Numerical Simulation Methods for Underwater Explosion with Centrifugal Tests

Abstract

e 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. e 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. e 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. e 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.

Study on Axial Dispersion Characteristics of Double-Layer Prefabricated Fragments

“…The above method only discusses the acceleration process of the fragment in the "detonation wave acceleration stage" and the "detonation wave product acceleration stage" [15], while the effect of the interaction between the layers on the fragments initial parameters is ignored [16]. Meanwhile, the difference in the fragments' initial parameters along the axis [17] and the applicability to the initial parameters of the double-layer prefabricated fragments [18][19][20][21] is not considered.…”

Similarity Law between Centrifuge Scale Test and Prototype Underwater Explosion

“…Song et al [11] conducted numerical simulation on the scale test of the underwater explosion of the centrifuge and discussed the applicability of the scale to the dynamic load of the underwater explosion. Wang et al [14] studied the law of underwater explosion shock wave and bubble pulsation under the additional acceleration of the centrifuge through the centrifuge scale model test and numerical simulation; they also analyzed the influence of the water equation of state and boundary conditions on the numerical simulation results. e use of grid size as the charge radius in the threedimensional model is recommended.…”