Analysis of the turbulence collapse in a closed channel with surface transient temperature conditions
Keywords:CFD, Intermittency, LES, Turbulence
AbstractNumericalFlow at the nocturnal atmospheric boundary layer, during the very stable ﬂow regime (VSBL), is complex due to the almost complete suppression of the ﬂow turbulence and its resurgence in the form of intermittent bursts of turbulence. The occurrence of intermittent ﬂow in the stable boundary layer (SBL) may be associated with external ﬂow phenomena such as low-level jets and wave phenomena. However, recent work suggests that intermittency may be a natural mode of VSBL, regimen when the ﬂow is laminarizing. Thus, the present work aims to simulate a situation of the continuous increase of the stratiﬁcation of the ﬂow by continuously reducing the surface temperature of the ﬂow in a closed channel. Numerical simulations were performed using large eddy simulation (LES), with a free software of computational ﬂuid dynamics OpenFOAM. The results indicate that as the temperature gradient increases between the surface and the top of the vertical domain, the boundary layer turbulence near the surface is reduced and a jet is generated in the ﬂow. In addition, as surface temperature decreases, intermittent events arise in the runoff.
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