Hydrodynamic cavitation of nematic liquid crystal in Stokes flow behind bluff body with different shapes in microchannel

Abstract

Hydrodynamic cavitation, which occurs when the local pressure is below the saturated vapor pressure in hydrodynamic flow, is ubiquitous in fluid dynamics and implicated in a myriad of industrial and biomedical applications. Although extensively studied in isotropic liquids, corresponding investigations in anisotropic liquids are largely lacking. In this paper, the hydrodynamic cavitation in the bluff body bypass flow of nematic liquid crystal 5CB in the microchannel is experimentally investigated. By 5CB, we mean the thermotropic liquid crystal 4′-pentyl-4-biphenylcarbonitrile. When the Reynolds number is in the range of 3 × 10−4 < Re < 1.2 × 10−3, a special flow phenomenon behind the bluff body is observed, namely, the disclination loop. The critical Reynolds number of cavitation inception varies with the shape of the bluff body, while the lowest value corresponds to the triangular bluff body. The hydrodynamic cavitation occurs in the Stokes flow regime with the Reynolds number significantly lower than 0.1 for all bluff bodies. There is a close relation between the oscillation behavior of cavitation domains and the structure of the bluff body. In addition, the pressure difference between the inlet and outlet of the microchannel shows linear relation with the Reynolds number rather than the quadratic relation for isotropic fluids, which proves the presence of shear thinning in the flow of nematic liquid crystals. The study in this paper on the hydrodynamic cavitation of nematic liquid crystal can broaden the research on providing new approaches for the enhancement of fluid mixing and heat transfer in microfluidic chips.