Abstract
The study describes recent simulation results for underwater explosions in close-proximity to rigid targets. Simulations are performed using Chinook, an Eulerian computational fluid dynamics (CFD) code. Predicted target loadings are compared with measurements taken from a series of experiments conducted under an international collaboration between Canada, The Netherlands, and Sweden. The simulations of the rigid target tests focused on the modelling of gas bubble collapse and water jetting behaviour. Both two-dimensional and three-dimensional simulations were performed. It was found that the two-dimensional analyses produced good bubble periods and reasonable impulse loading compared to experimental data. The time of arrival of the bubble collapse and water jetting were found to be very mesh dependent and refining the mesh did not always produce better results. The two-dimensional approach provides a good initial understanding of the problem for a reasonable computational effort. The three-dimensional simulations were found to produce improved impulse predictions. The numerical gas bubble radii time histories are also compared to empirical time histories.
Highlights
Underwater explosions (UNDEX) that are within twice the radius of the explosion gas bubble of a target are referred to as close-proximity explosions
The present study focuses on bubble formation and collapse due to the detonation of a high explosive, Composition 4 (C4), at various standoffs and charge sizes
The gas bubble period and collapse impulse loading for the small domain (SD) and large domain (LD) twodimensional models are shown in Table 5 and Fig. 7, respectively
Summary
Underwater explosions (UNDEX) that are within twice the radius of the explosion gas bubble of a target are referred to as close-proximity explosions. Klaseboer et al [17] investigated several cases of gas bubble formation and collapse using a three-dimensional bubble dynamics code based on the boundary element method (BEM) They considered explosions under free-field conditions, near a vertical rigid target, and below a resilient horizontal target. The present study focuses on bubble formation and collapse due to the detonation of a high explosive, Composition 4 (C4), at various standoffs and charge sizes It compares the results of an extensive numerical study conducted using the CFD code Chinook with measurements from a series of close-proximity underwater explosion tests conducted at FOI Grindsjon, using a rigid target plate. The accuracy of the simulations based on charge size and initial standoff are determined
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