Large eddy simulation of turbulent natural convection between symmetrically heated vertical parallel plates for water

Detailed flow development and indicators of transition in a natural convection flow in a vertical channel

“…A LES study of Kogawa et al [13] of a symmetrically heated channel, at uniform temperature associated the beginning of transition to the appearance of the Tollmien-Schlichting (TS) waves which are characteristics of the beginning of the natural transition of weakly disturbed natural convection flow [14], [15]. However, as was demonstrated by Fedorov and Viskanta [10] in a study using RANS models and by Lau et al [16] and Tkachenko et al [17] in LES investigations, the turbulent intensity level at the entrance of the channel proved crucial to obtaining a fairly good representation of the mean and turbulent quantities of the flow.…”

“…However, as was demonstrated by Fedorov and Viskanta [10] in a study using RANS models and by Lau et al [16] and Tkachenko et al [17] in LES investigations, the turbulent intensity level at the entrance of the channel proved crucial to obtaining a fairly good representation of the mean and turbulent quantities of the flow. Because of the presence of the inlet disturbances, the TS waves observed by Kogawa et al [13] are replaced by much more complex three-dimensional structures [7,18,19] which make their criteria impossible to use to locate the beginning of the transition.…”

“…A maximum yplus value of x + = 0.8 was obtained by using the maximum friction velocity, implying that viscous sub-layer had been sufficiently resolved. In the literature, similar grid resolutions have been used in numerical LES modeling of natural convection for which the transitional behavior of the flow was shown to be correctly modeled (see e.g [13],[23] [17]…”

Transitional natural convection flow in a vertical channel: Impact of the external thermal stratification

“…Despite that the transitional processes in natural convection flow induced by hot vertical plates have not been fully explained yet, it is commonly accepted to consider that shear stresses are one of the driving factors that triggers transition to turbulence (see e.g. [11,23,19,7]).…”

“…Despite natural convection vertical plate flows share some similitude with vertical channel flows; these two flows remains very different, regarding their velocity and thermal quantities as well as the transitional behavior (see e.g. [10,11]). That is why the direct comparison between these flows may be limited and must be carried with caution.…”