Single drop breakup in turbulent flow

Abstract

The breakup process of a single drop in homogeneous isotropic turbulence was studied using direct numerical simulations. A diffuse interface free energy lattice Boltzmann method was applied. The detailed visualization of the breakup process confirmed breakup mechanisms previously outlined such as initial, independent, and cascade breakups. High-resolution simulations allowed to visualize another drop breakup mechanism, burst breakup, which occurs when the mother drop has a large volume, and the flow is highly turbulent. The simulations indicate that the type of the breakup mechanism is a strong function of mother drop size and energy input. Large mother drops in highly turbulent flow fields are more likely to burst, producing a large number of drops of the size close to the Kolmogorov length scale. Small drops in moderate turbulence tend to break only once (initial breakup). The interfacial energy of a drop was tracked as a function of time during drop deformation and breakage. The maximum energy level of the deformed mother drop was compared to commonly used estimates of critical energy necessary to break a drop. Our results show that these reference levels of critical energy are usually underestimated. Moreover, in some cases even if the critical energy level was exceeded, the drop did not break because the time of the interaction between the drop and the eddies was not enough to finish the breakup. The numerical insight presented here can be used as a guideline for the selection of assumptions and simplifications behind breakup kernels.

Scaling of Droplet Breakup in High-Pressure Homogenizer Orifices. Part II: Visualization of the Turbulent Droplet Breakup

“…Cristini et al [33] investigated the break-up of droplets which are smaller than the Kolmogorov length of turbulence and are therefore only stressed by laminar shear flows and showed that, in addition to the elongation, the elongation duration is decisive. Komrakova [34] investigated droplet deformation and break-up of droplets exposed to isotropic turbulence and showed that the energy stored as surface energy until breakup can be different. Maniero et al [35] simulated the break-up of droplets in a system-specific high-pressure homogenizer with orifice and generated experimental results very similar to those obtained from the numerical model.…”

Sub-Kolmogorov droplet dynamics in isotropic turbulence using a multiscale lattice Boltzmann scheme

“…A lot of attention has been dedicated to droplet deformation and breakup in stationary laminar flows [8,13,14,15,16,17,18,19,20,11,10,21,22], but less is known about the dynamics of droplets in homogeneous isotropic turbulent flows, which pose the challenge of solving a multi-physics problem, since the flow properties of the turbulent scales have to be accurately transferred to the scale of the droplet. We can differentiate between two interesting cases for the deformation of droplets in homogeneous and isotropic turbulent flows [23]: On the one hand, there are studies on droplet dynamics on scales larger than the Kolmogorov scale [24,25,26,27,28]. On the other hand, we investigate the dynamics and breakup statistics of sub-Kolmogorov droplets, i.e.…”

A simple numerical method to simulate the flow through filter media: Investigation of different fibre allocation algorithms

“…This method uses a mesoscopic approach based on the Boltzmann equation to calculate macroscopic quantities (such as velocity and pressure fields). The LBM has proven to be a numerically efficient and accurate method to model fluid flow in complex geometric domains [22,23] and complex fluid modelling, [24,25] including for turbulence [26,27] and heat transfer. [28][29][30] In this method, the flow is calculated by updating the particle distribution functions by collision and streaming steps such as the following:…”