Bridging the Rossby number gap in rapidly rotating thermal convection

Journal of Fluid Mechanics, Год журнала: 2025, Номер 1010

Опубликована: Май 9, 2025

Geophysical and astrophysical fluid flows are typically driven by buoyancy strongly constrained at large scales planetary rotation. Rapidly rotating Rayleigh–Bénard convection (RRRBC) provides a paradigm for experiments direct numerical simulations (DNS) of such flows, but the accessible parameter space remains restricted to moderately fast rotation rates (Ekman numbers ${ {Ek}} \gtrsim 10^{-8}$ ), while realistic ${Ek}$ geo- applications orders magnitude smaller. On other hand, previously derived reduced equations motion describing leading-order behaviour in limit very rapid ( $ {Ek}\to 0$ ) cannot capture finite effects, physically most relevant part with small has remained elusive. Here, we employ rescaled rapidly incompressible Navier–Stokes (RRRiNSE) – reformulation Navier–Stokes–Boussinesq informed scalings valid ${Ek}\to , recently introduced Julien et al. (2024) provide full DNS RRRBC unprecedented strengths down {Ek}=10^{-15}$ below, revealing disappearance cyclone–anticyclone asymmetry unattainable Ekman ${Ek}\approx 10^{-9}$ ). We also identify an overshoot heat transport as is varied fixed $\widetilde { {Ra}} \equiv {Ra}{Ek}^{4/3}$ where $Ra$ Rayleigh number, associated dissipation due ageostrophic motions boundary layers. The validate theoretical predictions based on thermal layer theory show that solutions RRRiNSE agree . These results represent first foray into vast, largely unexplored rendered RRRiNSE.

Язык: Английский

---

Cascades transition in generalised two-dimensional turbulence

Journal of Fluid Mechanics, Год журнала: 2025, Номер 1008

Опубликована: Апрель 2, 2025

Generalised two-dimensional (2-D) fluid dynamics is characterised by a relationship between scalar field $q$ , called generalised vorticity, and the stream function $\psi$ ,namely $q = (-\nabla ^2)^{\frac {\alpha }{2}} \psi$ . We study transition of cascades in 2-D turbulence systematically varying parameter $\alpha$ investigating its influential role determining directionality (inverse, forward or bidirectional) these cascades. derive upper bounds for dimensionless dissipation rates energy $E_G$ enstrophy $\Omega _G$ as Reynolds number tends to infinity. These findings corroborate numerical simulations, illustrating inverse cascade $\alpha \gt 0$ contrasting with reverse behaviour \lt The dependence on system parameters reinforces observed transitions, substantiated spectral fluxes spectra, which hint at Kolmogorov-like scalings large scales but discrepancies smaller theoretical estimates. are possibly due non-local transfers, dominate we go from positive negative values Intriguingly, reveals similarities three-dimensional turbulence, notably emergence vortex filaments within framework, marking unique feature this model.

Язык: Английский

---

Critical behavior and multistability in quasi-two-dimensional turbulence

Physical Review Fluids, Год журнала: 2025, Номер 10(5)

Опубликована: Май 8, 2025

Язык: Английский

---

Turbulent mesoscale convection in the Boussinesq limit and beyond

International Journal of Heat and Fluid Flow, Год журнала: 2025, Номер 115, С. 109856 - 109856

Опубликована: Май 21, 2025

Язык: Английский

---