Macaroni-type breakup in the primary breakup of discontinuous shear-thickening suspension

Abstract

The primary breakup of discontinuous shear-thickening suspension is studied experimentally. A divergent nozzle was used as the annular passage of a coaxial two-fluid nozzle. The breakup morphology was observed with a DSLR camera and a high-speed camera. According to the experimental results, the discontinuous shear-thickening behavior and the geometry of the annular air nozzle of divergent section significantly affect the breakup morphology of the suspension jet. Under the action of the annular air, the suspension jet near the exit of the nozzle tends to expand radially and becomes hardened and incompressible in the axial direction. For discontinuous shear-thickening suspensions, the axial hardening does not affect the good fluidity in the radial direction because of their anisotropic microstructure. Therefore, a hollow structure appears, and the suspension jet exhibits the macaroni-type breakup. This breakup mode strengthens when the radial expansion increases. Based on the equation of continuity, the force analysis and mechanism of the macaroni-type breakup are discussed.