Investigation of Turbulent Entrainment‐Mixing Processes With a New Particle‐Resolved Direct Numerical Simulation Model
Abstract
A new particle‐resolved three‐dimensional direct numerical simulation model is developed that combines Lagrangian droplet tracking with the Eulerian field representation of turbulence near the Kolmogorov microscale. Six numerical experiments are performed to investigate the processes of entrainment of clear air and subsequent mixing with cloudy air and their interactions with cloud microphysics. The experiments are designed to represent different combinations of three configurations of initial cloudy area and two turbulence modes (decaying and forced turbulence). Five existing measures of microphysical homogeneous mixing degree are examined, modified, and compared in terms of their ability as a unifying measure to represent the effect of various entrainment‐mixing mechanisms on cloud microphysics. Also examined and compared are the conventional Damköhler number and transition scale number as a dynamical measure of different mixing mechanisms. Relationships between the various microphysical measures and dynamical measures are investigated to search for a unified parameterization of entrainment‐mixing processes. The results show that even with the same cloud water fraction, the thermodynamic and microphysical properties are different, especially for the decaying cases. Further analysis confirms that despite the detailed differences in cloud properties among the six simulation scenarios, the variety of turbulent entrainment‐mixing mechanisms can be reasonably represented with power law relationships between the microphysical homogeneous mixing degrees and the dynamical measures.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 19, 2018
- Source ID
- 10.1002/2017jd027507
Entities
People
- Chunsong Lu
- Xiaolin Li
- Yangang Liu
- Zheng Gao
Organizations
- Army Research Office
- Brookhaven National Laboratory
- Nanjing University of Information Science and Technology
- Stony Brook University
- United States Department of Energy