Turbulant Convection in a Fluid Heater from Below

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Non-Technical Abstract: Turbulent convection in a fluid heated from below occurs naturally in Earth's atmosphere and oceans where it influences climate and weather, in Earth's mantle where it contributes to the motion of continental plates, in Earth's outer core where it determines the magnetic field, in the Sun where it influences the temperature on Earth, and in many industrial processes where it may have significant economic consequences. This grant will support experiments under highly controlled laboratory conditions and in samples of idealized shapes where some of the central physical components of this process can be studied quantitatively. These components include relatively quiet fluid layers just above the bottom and below the top plate (the "boundary layers"), and a turbulent interior with highly fluctuating temperature and fluid-flow. A large convection cell, known as the "wind of turbulence", is superimposed on these interior fluctuations. Quantitative measurements will be made of the turbulent enhancement of the heat transport, of the temperature distribution in the interior, and of the wind dynamics. The highly quantitative experiments are of modest complexity and thus afford an exceptional diverse learning experience for both graduate and undergraduate students who participate in the work. Technical Abstract: Turbulent convection in a fluid heated from below occurs in many geophysical, astrophysical, and industrial situations. This grant will support experiments under highly controlled laboratory conditions and in samples of idealized, mostly cylindrical, shapes where some of the central physical components of this process can be studied quantitatively. These components include top and bottom boundary layers, and a turbulent interior with highly fluctuating temperature and velocity fields. A large-scale flow (LSC) is superimposed on the interior fluctuations. Quantitative measurements of heat transport will be made at the largest possible Rayleigh numbers (dimensionless temperature differences) in a search for an ultimate regime where extrapolation to astrophysical conditions may become possible. Studies of the temperature distribution in the interior and of the LSC dynamics will be undertaken. A theoretical model of the LSC dynamics will be developed. The highly quantitative experiments are of modest complexity and thus afford an exceptional diverse learning experience for both graduate and undergraduate students who participate in the work.