Shocked granular flow over multiple obstacles

Interaction of supersonic granular flow [1] with obstacles in a confined channel generates shock waves characterised by a nearly parabolic front of agitating grains in the outer region and a heap of static grains in the inner region. The inner static heap results from granular collapse due to high volume fraction and enhanced collision rate near the obstacle [2]. The present work reports interesting flow structures when granular shock waves are formed on an array of three identical wedges placed in line transverse to the flow direction in a rectangular chute at different symmetrical spacings. It is observed that spacing has a profound influence, resulting in three types of flow structures [3,4]. The experimental data showed a strong dependence of normalised shock stand-off distance on Froude number and normalised spacing. The normalised shock stand-off distance also followed a linear trend for a range of Froude numbers. Due to structural changes in the dynamic heap [3], a non-intuitive behaviour with wedge spacing is observed. These features will be discussed in detail using high-resolution shadowgraphy and velocity field obtained from particle imaging velocimetry.