No abstract

In this study, the complex phenomena of propagation and interaction of the blast waves impacting on obstacles were visualized and investigated using a numerical method. Three different distances between an immovable wall and a bomb shelter with a square block inside were considered while a blast source is located in front of wall at the same distance from shelter. The transitional shock phenomena were simulated by means of a multi-block mesh system and a flux computational model. Spatial discretization was performed using the Roe's upwind schemes; time integration was achieved via the second-order explicit Hancock method. Proof of the numerical results indicated that those results were in close agreement with the experimental data obtained for the wedge flow. For the cases proved, the geometries of the reflected wave patterns followed by the incident blast waves crossing the immovable wall and impacting inside of bomb shelters were similar. However the height of wall has a dominating impact on the effect associated with different incident blast waves from the same blast source. Meanwhile, different reflected overpressure-time histories and streamlines were observed and analyzed for the results obtained.

The moving bullet out of a rifle barrel is propelled by a fired explosive charge. Subsequently, a disturbed muzzle blast wave is initiated which lasts several milliseconds. In this study, axially symmetric, unsteady, Large Eddy Simulation (LES), and Ffowcs Williams and Hawkins (FWH) equations were solved by the implicit-time formulation. For the spatial discretization, second order upwind scheme was employed. In addition, dynamic mesh model was used to where the ballistic domain changed with time due to the motion of bullet. Results obtained for muzzle flow field and for noise recorded were compared with those obtained from experimental data; these two batches of results were in agreement. Five cases of gunshot including one model of an unsuppressed rifle and four models of suppressors were simulated. Besides, serial images of species distributions and velocity vectors-pressure contours in suppressors and near muzzle field were displayed. The sound pressure levels (dB) in far field that were post-processed by the fast Fourier transform (FFT) were compared. The proposed physical model and the numerical simulations used in the present work are expected to be extended to solve other shooting weapon problems with three-dimensional and complex geometries.

This study investigates the behavior of blast wave by employing the finite volume method to solve the associated three-dimensional, time-dependent, inviscous flow Euler equations. The numerical results are shown to be in good agreement with the experimental results obtained from shock tube flow studies. The results also identify the complex phenomena of flow structures, pressure distributions, and different types of reflected waves for closed-ended and open-ended bomb shelters.