Hydrodynamic cavitation in Stokes flow of nematic liquid crystal

Abstract

The impact of hydrodynamic cavitation is one of the key factors in the fabrication and application of metal materials. The hydrodynamic cavitation in anisotropic fluids can be much different from common fluids due to the unique fluid dynamics characteristics related to the director field. In this paper, the hydrodynamic cavitation of nematic liquid crystal 5CB flowing around a cylindrical pillar in a microchannel in the Stokes flow regime is studied at various Reynolds numbers and blockage ratios by experiments. Once the Reynolds number rises over a threshold value, the hydrodynamic cavitation of nematic liquid crystal is generated in the stokes flow in the microchannel, which is the unique phenomenon for anisotropic fluids. The critical Reynolds number of cavitation inception decreases with the increase of the blockage ratio. The Strouhal number is induced to describe this unsteady oscillating cavitation flow, while the Strouhal number increases and decreases with the increase of the blockage ratio and Reynolds number, respectively. Dynamics characteristics of the cavitation including cavity volume, oscillation frequency, and pressure difference are analyzed at different Reynolds numbers and blockage ratios by image binarization treatment and Fast Fourier Transformation analysis. The results of this study are useful for the application of microfluidic chips based on nematic liquid crystals and protection of devices in the environment of similar anisotropic fluids.