Coaxial air-blast exfoliation breakup of a quasi-solid paste jet

A series of novel phenomena emerges when the coaxial airflow rapidly blows over the quasi-solid paste jet surface, leading to the direct solid-like exfoliation breakup of protrusions on the side face and the liquid-like tensile breakup on the end face. The experimental findings unequivocally demonstrate that the vertical protrusion formation on the side face under high gas velocity serves as a precursor to the subsequent exfoliation breakup, while the tensile breakup is a consequence of axial elongation of the protrusions at the junction between the side and end faces. A crucial step in interpreting the exfoliation breakup is to discern the individual force competition at the jet interface. As gas velocity increases, the radial shear force maintains stronger than the axial drag force and becomes the dominant factor. After the formation of protrusions, the airflow component directly impacts the upper surface of the protrusion in a vertical manner and causes it to fracture similar to the cutting off of a rod-shaped solid. During tensile breakup, the protrusions on the end face develop into liquid threads, which rotate and elongate under axial airflow drag and reflux, ultimately leading to the breakup. Mathematical force models are established to elucidate this intriguing phenomenon observed in the experiments. This study of quasi-solid pastes in airflow will expand the new understanding of the interaction between gas, liquid, and solid states.