Dispersion of finite size droplets and solid particles in isotropic turbulence
- Author(s): Rosso, Michele
- Advisor(s): Elghobashi, Said
- et al.
Turbulent disperse two-phase flows, of either fluid/fluid or fluid/solid type, are common in natural phenomena and engineering devices. Notable examples are atmospheric clouds, i.e.
dispersed liquid water droplets and ice particles in a complex turbulent flow, and spray of fuel
droplets in the combustion chamber of internal combustion engines. However, the physics of
the interaction between a dispersed phase and turbulence is not yet fully understood. The
objective of this study is to compare the dispersion of deformable finite size droplets with
that of solid particles in a turbulent flow in the absence of gravity, by performing Direct
Numerical Simulation (DNS). The droplets and the particles have the same diameter, of the
order of the Taylor’s microscale of turbulence, and the same density ratio to the carrier flow.
The solid particle-laden turbulence is simulated by coupling a standard projection method
with the Immersed Boundary Method (IBM). The solid particles are fully resolved in space
and time without considering particle/particle collisions (two-way coupling). The liquid
droplet-laden turbulence is simulated by coupling a variable-density projection method with
the Accurate Conservative Level Set Method (ACLSM). The effect of the surface tension
is accounted for by using the Ghost Fluid Method (GFM) in order to avoid any numerical
smearing, while the discontinuities in the viscous term of the Navier-Stokes equation are
smoothed out via the Continuum Surface Force approach. Droplet/droplet interactions are allowed (four-way coupling). The results presented here show that in isotropic turbulence
the dispersion of liquid droplets in a given direction is larger than that of solid particles due
to the reduced decay rate of turbulence kinetic energy via the four-way coupling effects of