Pattern Formation in Inclined Layer Convection

Abstract

We report experiments on thermally driven convection in an inclined layer of large aspect ratio in a fluid of Prandtl number σ ≈ 1. We observed a number of new nonlinear, mostly spatio-temporally chaotic, states. At small angles of inclination we found longitudinal rolls, subharmonic oscillations, Busse oscillations, undulation chaos, and crawling rolls. At larger angles, in the vicinity of the transition from buoyancy-to shear-driven instability, we observed drifting transverse rolls, localized bursts, and drifting bimodals. For angles past vertical, when heated from above, we found drifting transverse rolls and switching diamond panes.

Localized Transverse Bursts in Inclined Layer Convection

“…Above a codimensiontwo point at θ c , the primary instability is due to this shear flow instead of buoyancy [11,12,13]. Interesting bursting behavior has been observed in the vicinity of this codimension-two point [8].…”

“…Above a codimensiontwo point at θ c , the primary instability is due to this shear flow instead of buoyancy [11,12,13]. Interesting bursting behavior has been observed in the vicinity of this codimension-two point [8].We perform experiments in high pressure CO 2 in an apparatus similar to that described in [14], modified to allow for inclination. The gas was at a pressure of (48.26 ± 0.01) bar regulated to ±0.005 bar with a mean temperature of (25.00 ± 0.05) • C regulated to ±0.3mK.…”

“…In the Letter, we characterize a recently discovered [8] bursting phenomenon in inclined layer convection (ILC) resulting from the presence of both buoyancy and shear instabilities. Two features are intriguing: spatially localized bursts of a characteristic size and the triggering of local disorder within the burst without completely destroying the underlying roll structure (see Fig.…”

Defect Turbulence in Inclined Layer Convection

“…For ǫ > ∼ 0.02, where ǫ ≡ ∆T /∆T c − 1, these longitudinal rolls are unstable to undulations [11,12]. While it was predicted theoretically that a perfect pattern of undulations is stable [13], a defect turbulent state of undulation chaos was found experimentally [14]. Recently, undulation chaos was also observed in numerical simulations of the Navier-Stokes equations when random initial conditions were used [13], while with controlled initial conditions undulations were found to be stable.…”

“…[14] for an inclination angle of θ = 30 • . The fluid was compressed CO 2 at a pressure of (56.5 ± 0.01) bar regulated to ±0.005 bar with a mean temperature of (28 ± 0.05) • C regulated to ±0.0003 • C. For these parameters, convection appeared at ∆T c = (1.763 ± 0.005) • C. The planform of the convection pattern was observed by the usual shadowgraph technique [16].…”