Study of the Interaction between a Shock Wave and a Cloud of Droplets

Introduction

The pressure histories obtained when a shock wave propagates into an air-solid particle medium is well known: the overpressure jump decreases, as the shock wave propagates into the mixture and is followed by a pressure build-up corresponding to the velocity relaxation processes. In the present paper, an air-water droplet mixture interacting with a shock wave has been studied and the comportment of the pressure traces was found significantly changed in comparison to the interaction with a air-solid particle mixture. This is attributed to the ability of the droplets to deform and fragment into finer ones. This phenomenon, known as secondary atomisation, widely reviewed by Gelfand[1] and by Guildenbecher[2], affects both the pressure histories and the impulse induced by the shock wave. We have previously studied the influence of the height of cloud of droplets on shock wave propagation [3]. In the present work, we focus our attention on the influence of the droplet diameter on the attenuation of shock wave propagating into the air-water mixture. Moreover, predictions obtained by 1D numerical simulations are compared to the experimental results. The necessity to introduce a secondary atomisation model to fit the experimental behaviour is then underlined.