TY - JOUR
T1 - High-speed X-ray imaging of a ball impacting on loose sand
AU - Homan, Tess
AU - Mudde, Rob
AU - Lohse, Detlef
AU - Van Der Meer, Devaraj
N1 - Publisher Copyright:
© Cambridge University Press 2015.
PY - 2015/7/22
Y1 - 2015/7/22
N2 - When a ball is dropped in fine very loose sand, a splash and subsequently a jet are observed above the bed, followed by a granular eruption. To directly and quantitatively determine what happens inside the sand bed, high-speed X-ray tomography measurements are carried out in a custom-made set-up that allows for imaging of a large sand bed at atmospheric pressures. Herewith, we show that the jet originates from the pinch-off point created by the collapse of the air cavity formed behind the penetrating ball. Subsequently, we measure how the entrapped air bubble rises through the sand, and show that this is consistent with bubbles rising in continuously fluidized beds. Finally, we measure the packing fraction variation throughout the bed. From this we show that there is (i) a compressed area of sand in front of and next to the ball while the ball is moving down, (ii) a strongly compacted region at the pinch-off height after the cavity collapse and (iii) a relatively loosely packed centre in the wake of the rising bubble.
AB - When a ball is dropped in fine very loose sand, a splash and subsequently a jet are observed above the bed, followed by a granular eruption. To directly and quantitatively determine what happens inside the sand bed, high-speed X-ray tomography measurements are carried out in a custom-made set-up that allows for imaging of a large sand bed at atmospheric pressures. Herewith, we show that the jet originates from the pinch-off point created by the collapse of the air cavity formed behind the penetrating ball. Subsequently, we measure how the entrapped air bubble rises through the sand, and show that this is consistent with bubbles rising in continuously fluidized beds. Finally, we measure the packing fraction variation throughout the bed. From this we show that there is (i) a compressed area of sand in front of and next to the ball while the ball is moving down, (ii) a strongly compacted region at the pinch-off height after the cavity collapse and (iii) a relatively loosely packed centre in the wake of the rising bubble.
KW - Complex fluids
KW - Granular media
KW - 2023 OA procedure
UR - http://www.scopus.com/inward/record.url?scp=84937773240&partnerID=8YFLogxK
U2 - 10.1017/jfm.2015.375
DO - 10.1017/jfm.2015.375
M3 - Article
SN - 0022-1120
VL - 777
SP - 690
EP - 706
JO - Journal of fluid mechanics
JF - Journal of fluid mechanics
ER -