  The two-phase mixing layer formed between parallel gas and liquid streams is
an important fundamental problem in turbulent multiphase flows. The problem is
relevant to many industrial applications and natural phenomena, such as
air-blast atomizers in fuel injection systems and breaking waves in the ocean.
The velocity difference between the gas and liquid streams triggers an
interfacial instability which can be convective or absolute depending on the
stream properties and injection parameters. In the present study, a direct
numerical simulation of a two-phase gas-liquid mixing layer that lie in the
absolute instability regime is conducted. A dominant frequency is observed in
the simulation and the numerical result agrees well with the prediction from
viscous stability theory. As the interfacial wave plays a critical role in
turbulence transition and development, the temporal evolution of turbulent
fluctuations (such as the enstrophy) also exhibits a similar frequency. In
order to investigate the statistical response of the multiphase turbulence
flow, the simulation has been run for a long physical time so that
time-averaging can be performed to yield the statistically converged results
for Reynolds stresses and the turbulent kinetic energy (TKE) budget. An
extensive mesh refinement study using from 8 million to about 4 billions cells
has been carried out. The turbulent dissipation is shown to be highly demanding
on mesh resolution compared to other terms in TKE budget. The results obtained
with the finest mesh are shown to be not far from converged results of
turbulent dissipation which allow us to obtain estimations of the Kolmogorov
and Hinze scales. The computed Hinze scale is significantly larger than the
size of droplets observed and does not seem to be a relevant length scale to
describe the smallest size of droplets formed in atomization.
