Effect of external forcing scheme on liquid–liquid dispersion in sustained homogeneous isotropic turbulence

We present a numerical study investigating the interaction between sustained (forced) homogeneous isotropic turbulence (HIT) and a liquid–liquid dispersion (two-phase flow). The direct numerical simulations of two-phase forced HIT are performed using the diffuse interface free energy lattice Boltzmann method. The range of Taylor’s Reynolds number for the single-phase HIT achieved is 24.4–181. The influence of liquid–liquid dispersion is assessed by performing a statistical analysis of the two-phase flow sustained by external forcing. We selected three different forcing schemes to contrast the effects of external forcing and liquid–liquid dispersion on HIT characteristics. A scale-by-scale analysis was performed to study the role of liquid–liquid dispersion on the forced HIT energy cascade. The presence of an interfacial tension force modifies the energy transfer mechanism. The interfacial tension force exhibits linear spatial coherence with nonlinear energy transfer and energy dissipation in a specific range of wavenumbers. Furthermore, the liquid–liquid dispersion increases the isotropy of the flow field compared to the single-phase flow at large wavenumbers. Flow visualization of the instantaneous vorticity field indicates that the flow domain in the two-phase is more concentrated with intense vorticity regions than its single-phase counterparts. We also evaluated the effects of the liquid–liquid dispersion on the alignment of vorticity with the strain rate. The insights presented in our study are important for further understanding the energy transfer mechanism in two-phase HIT and the implications of different forcing schemes to generate and sustain turbulence on this mechanism.