Shocks and Shock Interactions in Granular flow Past Circular Cylinder

Khan, Aqib; Hankare, Priyanka; Kumar, Sanjay; Kumar, Rakesh; Verma, Shivam; Prakash, Sute Piyush

doi:10.2514/6.2019-3075

Cited by 4 publications

(3 citation statements)

References 17 publications

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“…Therefore, granular flows easily become supersonic, even at speeds as low as 1 m s −1 , and exhibit shock waves (Heil et al 2004;Amarouchene & Kellay 2006;Khan et al 2020). Granular shocks can be produced in laboratories by placing obstacles, such as a triangular wedge, in a stream of granular material (Gray et al 2003;Gray & Cui 2007;Garai, Verma & Kumar 2019;Khan et al 2019Khan et al , 2022Patel et al 2022). These shock waves are characterised by abrupt change in velocity and packing fraction of grains across a shock front.…”

Section: Introductionmentioning

confidence: 99%

“…The present article investigates the formation of dynamic granular heaps past an array of three triangular obstacles in a quasi-two-dimensional channel. Such flows were recently investigated by Khan et al (2019Khan et al ( , 2020 with two wedges using the shadowgraphy flow visualisation technique. It was reported that, for larger spacings, separate shock waves are formed on both the wedges that interact in the central region resulting in the formation of a granular streak at the centre.…”

Section: Introductionmentioning

confidence: 99%

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Shocked confined-granular flow over obstacles

et al. 2023

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Interaction of supercritical granular flow with obstacles in a confined channel generates shock waves characterised by a nearly parabolic front of agitated 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. The present work reports interesting flow structures when granular shock waves are formed on an array of three identical triangular obstacles placed in a rectangular channel at different spacings. It is observed that spacing has a profound influence, resulting in three types of flow structures. Through dimensional analysis, it is found that the normalised shock stand-off distance primarily depends on the Froude number, $Fr$ , and the normalised spacing between the wedges. The experimental data show a strong dependence on these parameters. The normalised shock stand-off distance decreases linearly for small $Fr$ and asymptotically approaches a small value at high $Fr$ . The presence of a new stagnant dome-like structure results in a non-intuitive behaviour of shock stand-off with the wedge spacing. These features are discussed in detail using high-resolution shadowgraphy and the velocity field from particle image velocimetry.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shocked confined-granular flow over obstacles

et al. 2023

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“…For example, ripples from a stone dropped in the lake can be felt on far-off distances, whereas a stone dropped on a granular bed will create a localized crater (Marston, Li & Thoroddsen 2012) with disturbances confined to its close proximity. The formation of special patterns such as segregation (Ottino & Khakhar 2000;Goldhirsch 2003;Gray 2018), clusters (Savage 1992), oscillons (Umbanhowar, Melo & Swinney 1996;Aranson & Tsimring 2006), shock waves (Amarouchene, Boudet & Kellay 2001;Rericha et al 2001;Gray, Tai & Noelle 2003;Vilquin, Boudet & Kellay 2016;Garai, Verma & Kumar 2019;Tregaskis et al 2022) and granular streaks during shock-shock interactions (Khan et al 2019(Khan et al , 2020Johnson 2020) is, in fact, a direct or indirect consequence of dissipative effects during granular collisions.…”

Section: Introductionmentioning

confidence: 99%

Detachment of strong shocks in confined granular flows

et al. 2022

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Granular flows are highly dissipative due to frictional resistance and inelasticity in collisions among grains. They are known to exhibit shock waves at velocities that are easily achieved in industrial and nature-driven flows such as avalanches and landslides. This experimental work investigates the formation of strong shock waves on triangular obstacles placed in a dry rapid granular stream in a confined two-dimensional set-up. Oblique attached shock waves are formed for mild turning angles and higher flow velocities, whereas strong bow shock waves are formed for higher turning angles and slower granular streams. A shadowgraph imaging technique elucidates interesting characteristics of the shock waves, especially in the vicinity of shock detachment. Velocity distributions in the form of scatter plots and probability distribution functions are calculated from the flow field data obtained by particle imaging velocimetry. The flow field around the granular shock wave region represents a bimodal distribution of velocities with two distinct peaks, one representing the supersonic flow within the free stream, and the other corresponding to the subsonic faction downstream of a shock wave. Connecting the two is a population that does not directly belong to either of the modes, constituting the non-equilibrium shock wave region. The effect of grain size and scaling, for fixed free-stream conditions and fixed channel width, on the shock detachment is presented. The mechanisms of the static heap formation and the shock detachment process in a confined environment are discussed.

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A numerical investigation of granular shock waves over a circular cylinder using the discrete element method

et al. 2022

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Numerical simulation based on the discrete element method (DEM) is used to investigate the flow field generated when a cylindrical obstacle is placed in a supersonic granular stream. Robust validation of the simulation model is performed by comparing numerical results with experiments. Experiments are performed using a two-dimensional set-up generating rapid granular flow owing to gravity. DEM simulations demonstrate that a rapid gas-like stream of grains suddenly decelerates across the shock wave and finally collapses into a slow-moving heap at the cylinder. The volume fraction suddenly increases across the shock layer and remains constant thereafter. The flow physics of the shock wave and the granular heap is elucidated through fundamental fluid dynamic quantities such as the velocity, volume fraction, pressure and granular temperature. It is shown that the interaction of grains with a cylindrical obstacle results in the generation of pressure, which is responsible for sustaining static granular heaps on the cylinder. The total pressure is resolved into collisional and streaming components. A streaming pressure is generated owing to velocity fluctuations, and is found to be significant only in the shock wave region. The observations show that the rheological complexity offered by granular shock waves is a direct manifestation of the dissipative and frictional nature of granular collisions. The new insight into the granular heaps could be relevant to a variety of applications involving granular-fluid–solid interactions.

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Shocks and Shock Interactions in Granular flow Past Circular Cylinder

Cited by 4 publications

References 17 publications

Shocked confined-granular flow over obstacles

Shocked confined-granular flow over obstacles

Detachment of strong shocks in confined granular flows

A numerical investigation of granular shock waves over a circular cylinder using the discrete element method

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