부산대학교 도서관

Large-eddy simulations are carried out for a particle-laden vertical turbulent channel flow at Reynolds number of 180 based on friction velocity and channel half-width. To minimize the numerical and aliasing errors, a fourth-order compact finite-volume method in space and a fourth-order Runge-Kutta method in time along with a dynamic Smagorinsky model with explicit filter-grid size ratio 2 have been used to solve the filtered equations of the carrier flow. Heavy, small particle motion is governed by drag, gravitational, and Saffman lift forces in the Lagrangian frame. These particle equations are integrated in time using a second-order Adams-Bashforth method. The effect of subgrid-scale (SGS) fluctuations on particle statistics has been studied using two models available in the literature, with and without considering SGS velocity temporal correlation. In addition, a new model is implemented in this work to account for the anisotropy of flow. The results show that in the near-wall region the effect of SGS fluctuations on particle statistics is considerable, especially for small particle size of the order of 1μ m . The fluctuation levels of the wall-normal and spanwise directions of 1 - μ m lycopodium particle velocity are influenced strongly by SGS fluctuations and they are accentuated when the SGS effects are considered. The results for the 1 - μ m lycopodium particle show that the new model, which accounts for SGS anisotropy and Lagrangian temporal correlations of SGS fluctuations, yields improved results for particle turbulent intensity, especially in the near-wall region, when compared with other models. The effect of Saffman lift force on particle turbulent intensity is increased by increasing particle Reynolds number, especially in the wall-normal and spanwise directions. [ABSTRACT FROM AUTHOR]