Plenary Lecture

Modeling and Simulation of Inhomogeneous Stratified Turbulent Flows

Professor Albert F. Kurbatsky
Khristianovich Institute of Theoretical and Applied Mechanics
Russian Academy of Sciences, Siberian Branch and
Novosibirsk State University,
Russia, Novosibirsk
Email: kurbat@nsu.ru
 

Abstract: The modeling and simulation of the planetary boundary layer over land is a persistent, problematic feature in weather, climate, pollutant dispersion, and air quality topics. Planetary boundary layers are usually classified into three types: neutral, convective, and stable, based on its stability: buoyancy effects and the dominant mechanism of turbulence generation. Stable boundary layer turbulence has inevitable difficulties in numerical simulations (arising from small scales of motion due to stratification) and to the intrinsic complexity in its dynamics, e.g., occurrences of intermittency, Kelvin-Helmholtz instability, gravity waves, low-level jets, meandering motions, etc. Therefore is not surprising that today there is a general consensus among researches that our understanding of stable boundary layer (especially the very stable regime) is quite poor and even small future advances justify more work. To improve parameterization of stable boundary layer turbulence in this study is used so-called RANS approach for obtaining, nonlocal on-being, anisotropic expressions for turbulent fluxes of momentum and scalar. Numerical modeling of boundary layer evolution in all range from the convective to a stable state shows that such improved parameterization of turbulence allows to obtain for very stable regime (Richardson's number more than 0.25) that the turbulent Prandtl number stability dependent from the gradient Richardson's number (the result fixed by the laboratory measurements) that allows momentum to be transported by the internal waves, while heat diffusion is impeded by the stratification. This improvement alleviates the problem of over prediction of heat diffusion under stable conditions, which is a characteristic of conventional boundary-layer schemes, such as the Medium Range Forecast (MRF) employed in the mesoscale models such as the Penn State/NCAR Mesoscale Model (MM5).


Brief Biography of the Speaker:
The modeling and simulation of the planetary boundary layer over land is a persistent, problematic feature in weather, climate, pollutant dispersion, and air quality topics. Planetary boundary layers are usually classified into three types: neutral, convective, and stable, based on its stability: buoyancy effects and the dominant mechanism of turbulence generation. Stable boundary layer turbulence has inevitable difficulties in numerical simulations (arising from small scales of motion due to stratification) and to the intrinsic complexity in its dynamics, e.g., occurrences of intermittency, Kelvin-Helmholtz instability, gravity waves, low-level jets, meandering motions, etc. Therefore is not surprising that today there is a general consensus among researches that our understanding of stable boundary layer (especially the very stable regime) is quite poor and even small future advances justify more work. To improve parameterization of stable boundary layer turbulence in this study is used so-called RANS approach for obtaining, nonlocal on-being, anisotropic expressions for turbulent fluxes of momentum and scalar. Numerical modeling of boundary layer evolution in all range from the convective to a stable state shows that such improved parameterization of turbulence allows to obtain for very stable regime (Richardson's number more than 0.25) that the turbulent Prandtl number stability dependent from the gradient Richardson's number (the result fixed by the laboratory measurements) that allows momentum to be transported by the internal waves, while heat diffusion is impeded by the stratification. This improvement alleviates the problem of over prediction of heat diffusion under stable conditions, which is a characteristic of conventional boundary-layer schemes, such as the Medium Range Forecast (MRF) Professor Albert Kurbatsky received Master Sc degree in Physics from the Novosibirsk State University, Russia, in 1963. He obtained Ph.D. degree and then DSc (Phys. and Math.) degree from the Institute of Thermophysics of Russian Academy of Sciences, Siberian Branch, Russia, Novosibirsk, in 1975 and 1985, respectively. He is a Professor at the Department of Physics at the Novosibirsk State University, Russia, Novosibirsk and he is the Principal Scientific Researcher at the Khristianivich Institute of Theoretical and Applied Mechanics of Russian Academy of Sciences, Siberian Branch, Russia, Novosibirsk. Prof. Kurbatsky’s research work & interest include studies in modeling and simulation of complex turbulent flows in environment with application to the planetary boundary layer, in particular. He is author of over 160 publications mostly published in rigorously referred journals. He is author of two monographies on the turbulence modeling.employed in the mesoscale models such as the Penn State/NCAR Mesoscale Model (MM5).