Abstract
In the past half century, large eddy simulations (LESs) have played an important role in turbulent flow simulation and improving the performance of computing technology. To generate a fully developed turbulent boundary layer in the channel domain using LES, suitable inflow conditions along with turbulent characteristics are required. This study aimed to clarify the effect of the integral length scale on the generation of turbulent boundary layers. To accomplish this, an artificially created boundary layer was imposed on the inlet section, which gradually evolved into a fully developed turbulent boundary layer flow inside the numerical domain. In this study, the synthetic inflow method, which is a commonly employed technique, was used by imposing the spatial and temporal correlation between two different points on the inlet section. In addition, we conducted parametric length scale studies on the inlet section and compared our results with existing data. The results showed that the larger length scales in the spanwise direction were not only effective in achieving the target shape of a fully developed turbulent boundary layer, but also developed it faster than the smaller length scales.
Highlights
In a variety of engineering and basic scientific area, the turbulent boundary layers over smooth and rough wall surfaces have long been discussed and reported
Given that the synthetic inflow generator was available, the channel flow simulation on the large eddy simulations (LESs) platform was initially conducted with the aim of observing the development of the turbulent flow in the whole domain
The channel flow started with the data from the synthetic inflow generator, adopting it in the inlet section, and developed the flow downstream to the smooth wall-bounded channel
Summary
In a variety of engineering and basic scientific area, the turbulent boundary layers over smooth and rough wall surfaces have long been discussed and reported It is usually related with an increase in momentum transport, for example, see the literatures (Kovasznay [1], Willmarth [2], Kline et al [3], Sreenivasan [4] , Kline and Robinson [5], and Cermak and Cochran [6]). On the other hand, regarding large eddy simulation (LES), only the large scales are resolved, and the effects of the smallest scales are modeled This is because the large-scale eddies are known to be largely affected by the boundary conditions and should be computed, but small scales are largely independent of the flow geometry and tend to be homogeneous and isotropic, irrespective of the geometry being considered, and, can be modelled. LES requires less computational effort than that for DNS, and the computational requirements of the LES remain rather high for the optimization of complicated processes where a large number of computations need to be performed
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