Plume Fragmentation by Bulk Interactions in Turbulent Rayleigh-Bénard Convection

Measurements of the dynamics of thermal plumes in turbulent mixed convection based on combined PIT and PIV

“…closer to the bulk of the sample, leading to sharper temperature distributions around the mean fluid temperature in the bulk. This explanation is also in agreement with the findings from Bosbach et al (2012). They ascribe the fragmentation process of plumes to interactions with wall domains of the LSCs and turbulent bulk fluctuations.…”

“…Herein, the formation of swirls should also be visible. However, with increasing distance of the measurement plane to the thermal boundary layer, turbulent interactions with the bulk will more and more fragment the sheet-like plumes (see Bosbach et al 2012). Hence, an increase in this distance will raise the effect of the bulk interactions.…”

“…The reason might be that less sheet-like plumes are located in the measurement plane since the thickness of the thermal boundary layer decreases with increasing Ra. According to Bosbach et al (2012), the higher Ra leads to stronger velocity fluctuations in bulk, which fragments the sheet-like plumes. This process smears out the temperature fingerprint of the plume, and thus, the temperature deviation between plume and ambient fluid decreases.…”

“…a measurement position further away from the boundary layer. According to Bosbach et al (2012), the interactions of the sheet-like plumes with the turbulent fluctuations of the temperature and/or the velocity in the bulk lead to a fragmentation of the plumes. Since an increase in Ra implies stronger fluctuations, the sheet-like plumes are more fragmented than the former ones in case A05.…”

Dynamics of line plumes on horizontal surfaces in turbulent convection

“…the total length L p , under similar assumption that natural convection boundary layers, or equivalently line plumes that are an outcome of these boundary layers, carry most of the heat from the plate to the bulk. The plume lengths per unit area L p /A ∼ 1/Z w for any given fluid; a similar Ra 1/3 dependence were also observed by Bosbach et al (2012), eventhough they interpreted it differently. This result also implied that L p H/A ∼ N u, the Nusselt number; N u = Q/(k∆T /H), where Q is the heat flux.…”