Numerical simulation of underwater explosion loads

Abstract

Abstract：Numerical simulation of TNT underwater explosion was carried out with AUTODYN software. Influences of artificial viscosity and mesh density on simulation results were discussed. Detonation waves in explosive and shock wave in water during early time of explosion are high frequency waves. Fine meshes (less than 1,mm) in explosive and water nearby, and small linear viscosity coefficients and quadratic viscosity coefficients (0.02 and 0.1 respectively, 1/10 of default values) are needed in numerical simulation model. According to these rules, numerical computing pressure profiles can match well with those calculated by Zamyshlyayev empirical formula. Otherwise peak pressure would be smeared off and upstream relative errors would be cumulated downstream to make downstream peak pressure lower.Underwater explosion loads are important for antiblast design and analysis of naval ships. They are also input parameters for shock response analysis of naval ship structures and equipments. Precision description of underwater explosion loads affects the accuracy of vulnerability analysis directly. Many research results show that many numerical softwares in varying degrees, such as ALE3D, DYSMAS, DYTRAN, CTH, LS-DYNA, etc, have underestimated the peak pressure of shock wave. In order to approach peak pressure in far field underwater explosion calculated by empirical formula, Zhang et al [1] and Fang et al [2] promote significant parameters of equation of state for water while simulating TNT underwater explosion with DYTRAN software.

A mass‐fraction‐based interface‐capturing method for multi‐component flow

“…The EOS (27) for water is a piecewise function with respect to density. Thus, the value of w is necessary here and directly affects the expression of the EOS (27). Thus, the value of w is necessary here and directly affects the expression of the EOS (27).…”

“…Thus, the value of w is necessary here and directly affects the expression of the EOS (27). For piecewise Mie-Grüneisen EOS (27), it can be written in a simple polynomial form as follows [31,33]: As w is known, the expression of EOS for water can be confirmed and adapted to the equations system (19).…”

“…The piecewise form EOS as Equation (20) requires continuous p and at the turning points 1 , 2 , : : :, and it is always written in a Mie-Grüneisen form. Piecewise form EOS includes multistate Mie-Grüneisen EOS [25,26], polynomial EOS [27] and saturation EOS [28], and it is also frequently used for some special engineering problems (e.g., cavitation problem [28]). For multicomponent Riemann problem, the numerical model based on volume fraction or thermodynamical parameter always neglects the density of component [9,16].…”

“…in which there are [25] which means there is a strong shock wave with a high pressure ratio more than 10 5 . The EOS (27) for water is a piecewise function with respect to density. As the density of water w varies from 0 to the maximum value near the interface, there is an expression change of EOS.…”

“…As the density of water w varies from 0 to the maximum value near the interface, there is an expression change of EOS. Thus, the value of w is necessary here and directly affects the expression of the EOS (27). Here, the mass fraction of water y w is chosen to be the color function, and the density of water is evaluated by w D y w .…”