Structures of scalar transport in a turbulent channel

Abstract

Direct numerical simulation (DNS) of a turbulent channel with temperature treated as a passive scalar at a moderate Reynolds number (Re τ = 395) was performed to investigate the large scale motions responsible for scalar transport. Structures are elicited by three dimensional two-point correlations. Complete three dimensional structure of cross correlations between velocity and scalar fluctuations are evaluated for the first time. The results show that the organized motions which are responsible for transporting streamwise component of the turbulence kinetic energy, scalar variance, and streamwise heat flux are very similar only in the viscous sublayer. However, the large scale motions (LSM) which transport streamwise component of the turbulent kinetic energy, scalar variance, and streamwise heat flux are clearly distinct to each other beyond the buffer region. In addition, comprehensive three dimensional two-point correlation data imply that LSM which are responsible for carrying most of the Reynolds stresses are not exactly the same as those that transport most of the scalar fluxes in both inner and outer regions of the turbulent boundary layer. Analysis length scales of correlations revealed that the growth of LSM which influence both momentum and thermal transport is linear. Comparison of physical extents of LSM which are responsible for transporting Reynolds stresses and

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“…1979; Dharmarathne et al. 2016; Zhang, Hu & Zheng 2018; Chowdhuri, Todekar & Prabha 2021; Liu & Zheng 2021) that are similar to structures in the velocity field. Studying the influence of the fluid on the discrete particle phase and then revealing its structural characteristics in the high-Reynolds-number particle-laden wall-bounded turbulence can not only provide in-depth information on the transport behaviour of the fluid with respect to the particle but can also help to further reveal the physical mechanism of particle–turbulence interactions.…”

Application of a lattice Boltzmann method combined with a Smagorinsky turbulence model to spatially resolved heat flux inside a refrigerated vehicle

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Numerical semulations of flowing around of speed transport vehicle of type of MAGLEV

“…На сьогодні найбільш досконалою математичною моделлю в'язкої стисливої течії є рівняння Нав'є-Стокса. Правомірність їх використання підтверджується багаточисельними дослідженнями [3][4][5][6][7][8][9][10][11]. Фундаментальною основою їх використання є те, що просторово-часові масштаби турбулентності істотно переважають просторово-часові масштаби молекулярного руху.…”