Lateral Clearing of Far-Field Obliquely Reflected Blast Waves

The reflected blast pressure acting on a target is dependent both on the peak pressure of the travelling incident wave and the angle at which this wave impinges on the reflecting surface. Recent experimental work showed complex behaviour with regards to blast waves impacting rigid targets at large angles of incidence. Specifically, reductions in positive phase duration and impulse were seen. This paper presents the results from a series of numerical analyses using LS-DYNA to test the hypothesis that lateral velocities serve to ‘clear’ the reflected pressure along the face of the target, away from the source of the blast. First, the numerical model is validated using well controlled experiments of hemispherical PE4 charges detonated on a rigid, flat surface. Then, the numerical pressure, impulse and velocity histories were evaluated at various points on the target face and compared to those of a freely expanding blast wave, thereby giving a measure of the effect of angle of incidence. The results show that lateral clearing appears to be a contributing mechanism and has a marked effect on the duration of blast pressures acting on the target.