The Influence of Vertical Vorticity on Thermal Convection

Murphy, J. O.; Lopez, JM

doi:10.1071/ph840179

Cited by 13 publications

(14 citation statements)

References 2 publications

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“…The two bifurcating states are reflection-symmetry related. This is a well-known way to generate swirl via symmetry breaking, already observed in convection problems (Murphy & Lopez 1984;Massaguer, Mercader & Net 1990), and recently in localized heating in a cylindrical annulus (Navarro & Herrero 2011). In the present problem there is no swirl generation in the first bifurcation.…”

Section: Symmetriesmentioning

confidence: 64%

Instability of plumes driven by localized heating

Lopez

Marqués

2013

J. Fluid Mech.

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Plumes due to localized buoyancy sources are of wide interest owing to their prevalence in many situations. This study investigates the transition from laminar to turbulent dynamics. Several experiments have reported that this transition is sensitive to external perturbations. As such, a well-controlled set-up has been chosen for our numerical study, consisting of a localized heat source at the bottom of an enclosed cylinder whose walls are all maintained at a fixed uniform temperature, except for the localized heat source. At moderate Rayleigh numbers Ra, the flow consists of a steady, axisymmetric purely poloidal plume. On increasing Ra, the flow undergoes a supercritical Hopf bifurcation to an axisymmetric 'puffing' plume, where a vortex ring is periodically emitted from the localized heater. At higher Ra, this state becomes unstable to a sequence of symmetry-breaking bifurcations, going through a quasiperiodic 'fluttering' stage where the axisymmetric rings are tilted, and other states in which the sequence of tilted rings interact with each other. The sequence of symmetry-breaking bifurcations in the transition to turbulence culminates in a torus breakup event in which all the spatial and spatio-temporal symmetries of the system are broken.

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Section: Symmetriesmentioning

confidence: 64%

Instability of plumes driven by localized heating

Lopez

Marqués

2013

J. Fluid Mech.

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“…Nevertheless, it is still felt that the fluid will endeavour to transport heat in the most efficient manner, but it will also select the most stable mode which is compatible with efficiency. Murphy and Lopez (1984) demonstrated the existence of a new state which, although being less efficient than the usual state determined by the steady single-mode system of equations with hexagonal planform, has a number of properties rendering it the more stable of the two, and hence probably the preferred state. Murphy and Lopez (1984) made a detailed examination of this new state, concentrating on the effects of varying the Rayleigh and Prandtl numbers, with a fixed value of the horizontal wave number, on the steady state system.…”

Section: Introductionmentioning

confidence: 99%

Horizontal Wave Number Dependence of Type II Solutions in Rayleigh?Benard Convection with Hexagonal Planform

Lopez¹,

Murphy²

1984

Aust. J. Phys.

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The horizontal wave number dependence of the hexagonal planform solutions for the RayleighBenard convection problem, which have a nonzero vertical component of vorticity (type II solutions), has been established. Over the range of wave numbers which support cellular convection, comparisons between the thermal transport characteristics of these cyclonic type solutions and those traditionally obtained from nonlinear investigations of the single horizontal mode equations (type I solutions) have been made. From the numerical results obtained, it is found that the cell aspect ratio which maximizes the heat flux of type II solutions is larger than that for type I solutions, at quivalent parameter values, and that the value of the horizontal wave number giving maximum Nusselt number for type II solutions increases with Rayleigh number and decreases with Prandtl number.

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“…Theoretical investigations often either employ linearized Atmospheric Science Letters (2001Letters ( ) doi:10.1006Letters ( /asle.2001 1530-261X * c 2001 Royal Meteorological Society equations or a truncated nonlinear expansion, and generally do not present vertical vortices as solutions. One notable exception is Murphy and Lopez (1984) and Lopez and Murphy (1984), whose studies with a nonlinear``single-mode approximation'' revealed an onset of rotation in convection which had no Coriolis force or other vertical torques. A laboratory simulation of Rayleigh±Be Ânard convection in which vertical vortices were documented was carried out by Willis and Deardorff (1979).…”

Section: Introductionmentioning

confidence: 99%

Rayleigh‐Bénard convection as a tool for studying dust devils

Fiedler

Kanak

2001

Atmospheric Science Letters

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Intense columnar vortices in a convecting layer are explored with direct numerical simulations that are otherwise similar to the large-eddy simulations of Kanak et al. (2000. With free-slip boundaries and a Rayleigh number of 10 6 (4096 times critical), vortices similar to large dust devils are readily produced. The genesis, intensity and life cycle of these intense vortices (dust devils) are studied. The simulated dust devils last for the order of the over-turning time of the largest eddies. The intensity is limited by the hydrostatic pressure drop supported by the buoyancy con®ned in the core. The genesis of a simulated dust devil requires not only tilting of the baroclinically generated vorticity, but also a symmetry-breaking event that allows one sign of vorticity to become concentrated in an updraft. Such symmetry breaking is the rule with random initialization in the simulations. However, when initialization is restricted to certain Fourier modes, exceptions are found that produce only symmetric vortex couplets that are relatively weak.*

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The Influence of Vertical Vorticity on Thermal Convection

Cited by 13 publications

References 2 publications

Instability of plumes driven by localized heating

Instability of plumes driven by localized heating

Horizontal Wave Number Dependence of Type II Solutions in Rayleigh?Benard Convection with Hexagonal Planform

Rayleigh‐Bénard convection as a tool for studying dust devils

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