Shock and blast attenuation by aqueous foam barriers: influences of barrier geometry

A Free-Lagrange CFD code is used to simulate the attenuation, by means of barriers of aqueous foam, of shocks and blast waves emerging from the open end of a two-dimensional duct. A range of foam barrier configurations is explored, comprising foam sheets that extend the effective duct length, and foam "caps" that completely obstruct the duct exit. Near-field off-axis overpressure time-histories are presented for each configuration. Two attenuation mechanisms are identified, both of which are influenced by the barrier geometry used: partial transmission at foam/air interfaces due to impedance mismatching, and delay of blast waves within the foam. Attenuation by dissipation within the foam is not simulated.