Three-Dimensional Oblique Shock Diffraction Over a Rectangular Parallelepiped: Computational/Experimental Comparison

Three-dimensional, unsteady finite-difference calculations with the HULL hydrocode are used to describe the shock diffraction process resulting from a shock wave striking the front of a scaled model of an S-280 Electrical Equipment shelter at oblique incidence. The 52.5 degree obliquity of the incident 34.5 kPa 5 psi overpressure shock on the front face produces a peak reflected overpressure that is approximately 50 percent larger than that for normal reflection. The numerical calculations are discussed and evaluated by comparison with experimental pressure measurements taken in shock tube tests on a scale-model shelter. Difficulties are experienced in both the 3-D calculations and the experiment in resolving the peak reflected overpressure on the front face. Except for some disagreement in the values for peak overpressure on the shelter front and windward side faces, the comparisons between computed and experimentally measured pressure for all faces show good agreement. Three- dimensional and two-dimensional cell-size convergence studies are discussed which quantify the influence of cell size on the numerical results.