Abstract
Entropy generation rates in two-dimensional Rayleigh–Taylor (RT) turbulence mixing are investigated by numerical calculation. We mainly focus on the behavior of thermal entropy generation and viscous entropy generation of global quantities with time evolution in Rayleigh–Taylor turbulence mixing. Our results mainly indicate that, with time evolution, the intense viscous entropy generation rate and the intense thermal entropy generation rate occur in the large gradient of velocity and interfaces between hot and cold fluids in the RT mixing process. Furthermore, it is also noted that the mixed changing gradient of two quantities from the center of the region to both sides decrease as time evolves, and that the viscous entropy generation rate and thermal entropy generation rate constantly increase with time evolution; the thermal entropy generation rate with time evolution always dominates in the entropy generation of the RT mixing region. It is further found that a “smooth” function and a linear function are achieved in the spatial averaging entropy generation of RT mixing process, respectively.
Highlights
Rayleigh–Taylor (RT) instability occurs in a large number of engineering applications
We mainly focus on the statistics of viscous and thermal entropy generation in RT turbulence mixing with time evolution
Entropy generation rates in two-dimensional Rayleigh–Taylor turbulence mixing with time evolution are investigated
Summary
Rayleigh–Taylor (RT) instability occurs in a large number of engineering applications. Entropy 2018, 20, 738 where Su and Sθ represent the direct viscosity and thermal entropy generation rate They mainly measure the magnitudes of gradients of the temperature and velocity fields. Based on the above discussions, the statistics of the viscosity and thermal entropy generation rates in two-dimensional RT turbulence by means of data obtained from the lattice Boltzmann method are investigated in this paper. We mainly focus on the statistics of viscous and thermal entropy generation in RT turbulence mixing with time evolution. LBM encompasses their fully local stream-and-collide nature, and possesses the potential advantage that the transfer of all information is local in time and space; the lattice Boltzmann equation is an effective approach to implement parallel computing.
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