Classical and symmetrical horizontal convection: detaching plumes and oscillations

Abstract

Classical and symmetrical horizontal convection is studied by means of direct numerical simulations for Rayleigh numbers Ra up to 3 × 10 12 and Prandtl numbers Pr = 0.1, 1 and 10. For both set-ups, a very good agreement in global quantities with respect to heat and momentum transport is attained. Similar to Shishkina & Wagner (Phys. Rev. Lett., vol. 116, 2016, 024302), we find Nusselt number Nu versus Ra scaling transitions in a region 10 8 Ra 10 11 . Above a critical Ra, the flow undergoes either a steady-oscillatory transition (small Pr) or a transition from steady state to a transient state with detaching plumes (large Pr). The onset of the oscillations takes place at Ra Pr −1 ≈ 5 × 10 9 and the onset of detaching plumes at Ra Pr 5/4 ≈ 9 × 10 10 . These onsets coincide with the onsets of scaling transitions.

Regime transitions in thermally driven high-Rayleigh number vertical convection

“…Such observation of scaling transitions further demonstrates that there are no pure scaling laws in thermal convection. This has already been seen in RBC (Grossmann & Lohse 2000;Ahlers et al 2009), horizontal convection Shishkina & Wagner 2016;Reiter & Shishkina 2020) and internally heated convection (Wang et al 2020b), and apparently crossovers between different scaling regimes also occur here. However, the sharpness of the scaling transition from β = 1/4 to β = 1/3 observed here is quite different from the smooth transition seen in RBC.…”

Thermal boundary-layer structure in laminar horizontal convection

“…This suggests that the rest of the HC flow remains to be rather laminar. The change of the scaling form in the hot region with growing is consistent with the change of the dependence on observed by Reiter & Shishkina (2020).…”

“…For , the Nusselt number can be approximately expressed by . Recent DNS results (Reiter & Shishkina 2020) revealed that the heat transport dynamics undergoes several transitions from steady state to chaotic state as increases. For , the data start to oscillate at and transit to a chaotic state at .…”

“…Moreover, as it was shown recently in Wang, Lohse & Shishkina (2021), HC is closely related to internally heated convection, where the thermal driving is not due to specific thermal boundary conditions but a bulk thermal source. A number of recent theoretical, experimental and numerical studies are dedicated to the transport properties and large-scale circulation in HC under various boundary conditions (Wang & Huang 2005;Sheard & King 2011;Griffiths, Hughes & Gayen 2013;Shishkina, Grossmann & Lohse 2016;Shishkina & Wagner 2016;Passaggia et al 2017a;Passaggia, Scotti & White 2017b;Shishkina 2017;Wang, Huang & Xia 2018;Ramme & Hansen 2019;Reiter & Shishkina 2020;Tsai et al 2020). However, current understanding of the thermal BL structure in HC remains rather limited.…”

“…2016; Passaggia et al. 2017 a ; Passaggia, Scotti & White 2017 b ; Shishkina 2017; Wang, Huang & Xia 2018; Ramme & Hansen 2019; Reiter & Shishkina 2020; Tsai et al. 2020).…”