Abstract
Time evolution features of kinetic and thermal entropy generation rates in turbulent Rayleigh-Bénard (RB) convection with mixed insulating and conducting boundary conditions at Ra = 109 are numerically investigated using the lattice Boltzmann method. The state of flow gradually develops from laminar flow to full turbulent thermal convection motion, and further evolves from full turbulent thermal convection to dissipation flow in the process of turbulent energy transfer. It was seen that the viscous, thermal, and total entropy generation rates gradually increase in wide range of t/τ < 32 with temporal evolution. However, the viscous, thermal, and total entropy generation rates evidently decrease at time t/τ = 64 compared to that of early time. The probability density function distributions, spatial-temporal features of the viscous, thermal, and total entropy generation rates in the closed system provide significant physical insight into the process of the energy injection, the kinetic energy, the kinetic energy transfer, the thermal energy transfer, the viscous dissipated flow and thermal dissipation.
Highlights
The Rayleigh–Bénard (RB) convection is one of most classical natural convections [1,2,3,4,5], which widely occur in a range of natural and industrial applications [1,2], such as in the Earth’s core and mantle, atmosphere, oceans and stars, nuclear reactors, crystallization processes, solar heating devices and so on
Our work mainly focuses on the effect of the mixed insulating and conducting boundary conditions on the time evolution features of thermal plumes, the viscous, thermal and total entropy generation rates
The The analysis of temperature field, flowflow streamlines, andand various entropy generation ratesrates willwill be be discussed with spatial-temporal evolution respectively
Summary
The Rayleigh–Bénard (RB) convection is one of most classical natural convections [1,2,3,4,5], which widely occur in a range of natural and industrial applications [1,2], such as in the Earth’s core and mantle, atmosphere, oceans and stars, nuclear reactors, crystallization processes, solar heating devices and so on. A wide variety of thermal plumes caused by the buoyancy in turbulent RB convection with mixed insulating and conducting boundary conditions play dominant role in the heat transfer. Once time evolution of the heat transfer has been described and understood in classical turbulent RB convection, the time evolution features of kinetic and thermal entropy generation rates in turbulent RB convection with mixed insulating and conducting boundary conditions still be further expanded. Our work mainly focuses on the effect of the mixed insulating and conducting boundary conditions on the time evolution features of thermal plumes, the viscous, thermal and total entropy generation rates. The physical insight features of kinetic and thermal entropy generation rates with time evolution are discussed in in turbulent RB convection with the mixed insulating and conducting boundary conditions, which mainly tried to understand the dynamics of fluid.
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