[GTP] Turbulent Collision-Coalescence of Cloud Droplets:, Simulation, Parameterization, and Application, Professor Lian-Ping Wang

[Silvia Gentile]

Turbulent Collision-Coalescence of Cloud Droplets:
Simulation, Parameterization, and Application
Professor Lian-Ping Wang
Department of Mechanical Engineering
University of Delaware

Over the last 15 years, effects of turbulence on collision-coalescence 
rate of cloud droplets have been actively studied through direct 
numerical simulations, stochastic modeling, and experimental 
measurements. This is motivated by the belief that air turbulence can 
enhance the growth of cloud droplets in situations where neither the 
condensational growth nor gravitational collision-coalescence growth is 
effective. Qualitatively, it has been argued that air turbulence can 
enhance the relative motion between the droplets through turbulent shear 
and fluid acceleration and inertial-induced clustering, as well as alter 
the local hydrodynamic interaction and the settling velocity, each of 
which could potentially increase the collision kernel relative to the 
gravitational kernel. The key issue is to obtain a quantitative 
assessment of level of enhancements by turbulence. In this talk, I will 
provide a comprehensive review of the current quantitative 
understanding. In some cases, I argue that we now have good estimates of 
the lower and upper bounds of the enhancements. The more specific 
questions on the effect of turbulence intermittency and limitations of 
DNS and other stochastic approaches will also be addressed. By combining 
various approaches, a more complete description of turbulent 
collision-coalescence of cloud droplets will likely emerge. Efforts to 
parameterize the different enhancements and to assess their impacts on 
warm rain development will be briefly discussed.
Brief bio: Lian-Ping Wang is currently Professor of Mechanical 
Engineering, and Joint Professor of Physical Ocean Science and 
Engineering in College of Earth, Ocean, and Environment at University of 
Delaware. Dr. Wang received his Ph.D. in Mechanical Engineering from 
Washington State University in 1990 and did post-doctoral work in 
turbulent dispersed flows at Brown University and Pennsylvania State 
University before joining University of Delaware in 1994. Dr. Wang uses 
advanced simulation tools and theoretical methods to study multiphase 
flows and transport in engineering applications and environmental 
processes. He is currently developing computational tools to study 
collision rates and growth of cloud droplets in atmospheric clouds and 
its impact on warm rain initiation. He also develops numerical methods 
to study complex fluid flow and transport in fuel cells and soil porous 
media, and transport and retention of colloids and nanoparticles in the 
subsurface environment.

Thursday, 21 July 2011, 3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Small Seminar Room 1001

-- 
Silvia Gentile
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 803035
www2.image.ucar.edu/IMAGe