Structure and dynamics of small-scale turbulence in vaporizing two-phase flows

Area of Science:

• Fluid dynamics
• Turbulence research
• Multiphase flow analysis

Background:

• Understanding multiphase turbulent flows is crucial for industrial and geophysical applications.
• The topology of local flow in vaporizing forced homogeneous isotropic turbulent two-phase flows requires further investigation.

Purpose of the Study:

• To investigate the topology of local flow in vaporizing turbulent two-phase flows.
• To analyze the behavior of flow invariants at varying distances from the liquid-gas interface.

Main Methods:

• Direct numerical simulations (DNS) were employed.
• Invariants of velocity-gradient, rate-of-strain, rate-of-rotation tensors, and scalar gradient were computed.
• Schur decomposition of the velocity gradient tensor was used.

Main Results:

• Joint probability density functions of invariants show classical shapes in carrier-gas regions, changing near the liquid-gas interface.
• Flow topology near the liquid-gas interface resembles the viscous sublayer of turbulent wall-bounded flows.
• Spatial changes in vorticity and scalar gradient alignment were observed, with universal behavior far from the interface.

Conclusions:

• The study elucidates the distinct flow topology near liquid-gas interfaces in vaporizing two-phase flows.
• Non-normal effects of the velocity gradient tensor are critical for explaining preferred alignment phenomena.
• Findings contribute to a fundamental understanding of multiphase turbulent flow dynamics.