Convection under rotation for Prandtl numbers near 1: Linear stability, wave-number selection, and pattern dynamics
- Department of Physics and Center for Nonlinear Sciences, University of California, Santa Barbara, California 93106 (United States)
Rayleigh-Benard convection with rotation about a vertical axis was studied with the shadowgraph imaging method up to a dimensionless rotation rate {Omega} of 22. Most of the results are for a cylindrical convection cell with a radius-to-height ratio {Gamma}=40 that contained CO{sub 2} at 33.1 bars with a Prandtl number {sigma}=0.93. Measurements of the critical Rayleigh number R{sub c} and wave number k{sub c} for 0{lt}{Omega}{lt}22 agree well with predictions based on linear stability analysis. Above onset and with rotation, the average wave number and details of the pattern dynamics were studied. For {Omega}{approx_lt}5, the initial onset was to a pattern of straight or slightly curved rolls. For 0.1{approx_lt}{epsilon}{equivalent_to}{Delta}T/{Delta}T{sub c}{minus}1{approx_lt}0.5 but below the onset of spiral-defect chaos, rotation with {Omega}{approx_lt}8 produced weak perturbations of nonrotating patterns. Typically, this gave an S-shaped distortion of the zero-rotation pattern of straight or somewhat curved rolls. Rotation had a stronger effect on the source and motions of dislocation defects. For {Omega}{gt}0 the defects were generated primarily at the wall, whereas for {Omega}=0 they were nucleated in the bulk via the skewed-varicose instability. Rotation picked a preferred direction of motion for the defects once they formed. For {epsilon}{approx_gt}0.5, recognizable spiral-defect chaos and the oscillatory instability were observed for {Omega}{approx_lt}12. For {Omega}{ge}8, domain growth and front propagation suggestive of the Kueppers-Lortz instability were observed from onset up to an {epsilon} value that increased with {Omega}. Increasing {epsilon} at fixed {Omega}{approx_lt}12 enhanced dislocation-defect dynamics over Kueppers-Lortz front propagation. Quantitative measurements of average pattern wave numbers, correlation lengths, and spatially averaged roll curvature as functions of {epsilon} and {Omega} are presented. (Abstract Truncated)
- OSTI ID:
- 657416
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 55, Issue 6; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Convection for Prandtl numbers near 1: Dynamics of textured patterns
Square Patterns in Rayleigh-Benard Convection with Rotation about a Vertical Axis