Evolution and Features of Dust Devil‐Like Vortices in Turbulent Rayleigh‐Bénard Convection—A Numerical Study Using Direct Numerical Simulation

Abstract

First direct numerical simulations of dust devil-like structures for Rayleigh numbers up to 10 11 are presented• Dust devils are strongly affected by Rayleigh number and surface friction but less affected by the aspect ratio of the model domain• The 3-D structure of simulated dust devils is very similar to the one in large-eddy simulations of the atmospheric boundary layer

Evolution and Features of Dust Devil‐Like Vortices in Turbulent Rayleigh‐Bénard Convection—An Experimental Study

“…The overestimation in the range of the vortex radius R 0 is a typical property of this model (Sinclair, 1973). This result is also in good agreement with the simulation of Giersch and Raasch (2021). The pressure drop according to the Rankine vortex $${p}_{R}^{\ast }$$ can be calculated using Equation with density of air ϱ = 1.169 kg m −3 (Giersch & Raasch, 2021; Stephan et al., 2019).…”

“…Within an observation period of 2 hr (this is the period whose analysis has already been finished), we could detect 56 dust devil‐like vortices in total. Their properties coincide quite well with those structures identified in very recent DNSs by Giersch and Raasch (2021). As well, they show similarity to atmospheric dust devils.…”

“…A few streamlines lead directly into the bottom (z = 0 m), which is, presumably, an artifact of the fine-scale reconstruction algorithm. The pressure drop of about 150 mPa is of the same order of magnitude as in simulations (Giersch & Raasch, 2021), but up to four orders of magnitude smaller than for terrestrial dust devils (Metzger, 1999;Tratt et al, 2003).…”

“…Finally, we wish to compare the experimental data with data obtained from DNS of turbulent RBC (Giersch & Raasch, 2021). In the simulation, the spatial resolution of the obtained velocity field is higher than in our measurements, and thus, much more smaller vortices could be detected.…”

Large eddy simulations of the accumulation of buoyant material in oceanic wind-driven and convective turbulence

“…The peak vertical velocity occurs on the periphery of the convective vortex and encircles a local minimum in the centre. This is consistent with simulations of dust devils in the atmosphere (Raasch & Franke 2011;Giersch & Raasch 2021), which speculate that the decrease in vertical velocity in the central core of an averaged vortex could indicate stagnation points or flow reversal inside dust devils, shown schematically in Balme & Greeley (2006). Such features may be observable in instantaneous data with higher resolution, but this is outside the scope of the current study.…”