Effect of thixotropy on primary jet breakup – A DNS study

In the current study, round thixotropic jets injected into stagnant gas are investigated using direct numerical simulations (DNS). The Volume-of-Fluid (VOF) method is employed to capture the interface between the two phases. The thixotropic flow behavior is modeled by a kinetic rate equation for the microstructural integrity. The advection of the structural parameter λ is carried out in a flux-consistent manner, that is, the VOF fluxes are used to calculate the fluxes of λ , as recently proposed in the literature. A parametric study is conducted to determine the effect of thixotropy on the primary breakup mechanism. Starting from a thixotropic baseline configuration, the destruction parameter β and the thixotropic time scale τ θ are varied. The results are also compared with two Newtonian cases. The findings indicate that the thixotropic flow behavior has a significant effect on the instantaneous viscosity and therefore, the extent of breakup. However, the first- and second-order statistics of the velocity and the liquid phase volume fraction exhibit only slight differences. In addition, the viscosity of the liquid phase at the gas–liquid interface influences the number of droplets produced. • Primary breakup of round thixotropic jets into stagnant gas. • Breakup intensity depends on thixotropic model parameters. • Strong thixotropic effects are identified in the near-nozzle region and at the gas–liquid interface. • First- and second-order statistics of velocity and liquid phase volume fraction remain similar for all investigated cases. • Liquid phase viscosity at the interface plays a crucial role in defining breakup intensity and number of droplets produced.