Turbulent Mixing in Explosions

The report focuses on an experimental investigation of the dynamics of turbulent flow field features that arise from the detonation of a charge. The three main features covered are: * the detonation products cloud due to a freefield or 1-D confined, 2-D freefield detonation, * the (inert) products jet ejected from a detonation inside a chamber with an outlet opening and, * an explosive-driven turbulent jet of combustible gas ejected from a small chamber into a wider one. The experiments were carried out at laboratory scale, employing Nitropenta (PETN) charges of about 0.5 g. The main diagnostics were cinematographic high-speed shadow photography and pressure measurements. The main findings are that in the long-wavelength regime the spatial characteristics of the turbulent products cloud depend on the geometry (3-D freefield detonation not equal to 1-D-confined detonation). Experiments in the two chamber system with a combustible jet showed that the turbulent mixing in an explosive-driven jet facilitates combustion, which results in an additional pressure increase. An estimate of the buming rate which is essentially governed by the amount ot turbulent mixing can be inferred from the time-history of the average ressure in the system. Text in English.