On the entry of cylindrical disks into non-Newtonian fluid mixtures

A series of laboratory experiments was conducted to investigate solid object characteristics and fluid properties on the free fall of cylindrical disks into stagnant non-Newtonian ambient. The viscosity and yield stress of the ambient fluid mixtures were controlled by adjusting the concentration of a polymer. Six different fluid mixtures were prepared to develop a relatively wide range of fluid viscosities and yield stresses to examine the behavior of free-falling disks in accordance with the variations in the disk's geometry, density, and mixture parameters. The effects of disks’ parameters, such as disk aspect ratio and relative density, on crown formation, pinch-off characteristics, and splash evolution were studied. Experimental results indicated that increasing the disk's density increased the pinch-off depth while a reduction in aspect ratio increased the pinch-off depth. The sinking time diminished with increasing the aspect ratio of disks, and such observations were independent of the rheological characteristics of the fluid mixture. The same devaluation was also experienced for the height of the crown. As the disk's density reduced, the splash curtain became smoother and the waves’ intensity attenuated. The energy losses were found to be correlated with the aspect ratio, density, and fluid viscosity. The augmentation of energy losses was linked with different parameters such as aspect ratio, disk density, and ambient fluid viscosity.