Intensified heat transfer in modulated rotating Rayleigh–Bénard convection

Geurts, BJ Bernard; Kunnen, Rudie

doi:10.1016/j.ijheatfluidflow.2014.04.007

Cited by 15 publications

(11 citation statements)

References 16 publications

(21 reference statements)

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“…Conversely, at stages close to a rapidly collapsing Nusselt number, high turbulent fluctuation levels are seen throughout the entire flow domain and not just in the shear layers. This was also observed in case of modulated rotation without imposed large-scale flow reversals in [20].…”

Section: Fast and Slow Dynamics Of Heat Transfersupporting

confidence: 69%

“…In other words, the cylinder changes rotation about its vertical axis from clockwise to counter-clockwise and back, and does so periodically with a pre-specified frequency. This extends a previous study in which effects of modulated rotation were investigated in situations in which the direction of the rotation vector was kept the same, i.e., the rotation direction was always kept counter-clockwise [20]. Downloaded by [Eindhoven Technical University] at 00:35 07 January 2015…”

Section: Introductionsupporting

confidence: 68%

“…This was not selected here as mainly the characteristic qualitative impressions were the point of focusfor that purpose the choice t = 200 is adequate. We observe that the fragmentation of the velocity contours is more intense compared to the situation we studied in [20]. In that work, the rotation was modulated such that at any point in time the rotation was maintained …”

Section: Qualitative Flow-structure Changes Under Modulated Rotation mentioning

confidence: 71%

“…In this section, we first detail the mathematical model used to formulate turbulent flow in a rotating Rayleigh-Bénard configuration (Section 2.1, closely following [5,20]). Subsequently, we specify the numerical set-up (Section 2.2).…”

Section: Governing Equations and Numerical Methodsmentioning

confidence: 99%

“…The DNS is based on an extension of the method by [21][22][23] [21]. [20]. In cylindrical coordinates (r, φ, z) with r and φ denoting the radial and circumferential coordinates, respectively, the governing equations (8) possess terms that include a factor 1/r.…”

Section: Numerical Set-up and Spatial Resolutionmentioning

confidence: 99%

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Rotating turbulent Rayleigh–Bénard convection subject to harmonically forced flow reversals

Geurts

Kunnen

2014

Journal of Turbulence

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The characteristics of turbulent flow in a cylindrical Rayleigh-Bénard convection cell which can be modified considerably in case rotation is included in the dynamics. By incorporating the additional effects of an Euler force, i.e., effects induced by nonconstant rotation rates, a remarkably strong intensification of the heat transfer efficiency can be achieved. We consider turbulent convection at Rayleigh number Ra = 10 9 and Prandtl number σ = 6.4 under a harmonically varying rotation, allowing complete reversals of the direction of the externally imposed rotation in the course of time. The dimensionless amplitude of the oscillation is taken as 1/Ro * = 1 while various modulation frequencies 0.1 ≤ Ro ω ≤ 1 are applied. Both slow and fast flow-structuring and heat transfer intensification are induced due to the forced flow reversals. Depending on the magnitude of the Euler force, increases in the Nusselt number of up to 400% were observed, compared to the case of constant or no rotation. It is shown that a large thermal flow structure accumulates all along the centreline of the cylinder, which is responsible for the strongly increased heat transfer. This dynamic thermal flow structure develops quite gradually, requiring many periods of modulated flow reversals. In the course of time, the Nusselt number increases in an oscillatory fashion up to a point of global instability, after which a very rapid and striking collapse of the thermal columnar structure is seen. Following such a collapse is another, quite similar episode of gradual accumulation of the next thermal column. We perform direct numerical simulation of the incompressible Navier-Stokes equations to study this system. Both the flow structures and the corresponding heat transfer characteristics are discussed at a range of modulation frequencies. We give an overview of typical time scales of the system response.

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Section: Fast and Slow Dynamics Of Heat Transfersupporting

confidence: 69%

Section: Introductionsupporting

confidence: 68%

Section: Qualitative Flow-structure Changes Under Modulated Rotation mentioning

confidence: 71%

Section: Governing Equations and Numerical Methodsmentioning

confidence: 99%

Section: Numerical Set-up and Spatial Resolutionmentioning

confidence: 99%

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Rotating turbulent Rayleigh–Bénard convection subject to harmonically forced flow reversals

Geurts

Kunnen

2014

Journal of Turbulence

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On trigonometric cosine, square, sawtooth, and triangular wave‐type rotational modulations on triple‐diffusive convection in salted water

et al. 2021

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The onset of Rayleigh–Bénard convection and heat transfer under two‐frequency rotation modulation

Mathew

Pranesh

2021

Heat Trans

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The impact of 16 combinations of sinusoidal (sine) and nonsinusoidal (square, triangular, and sawtooth) timeperiodic Coriolis force (rotation modulation) on Rayleigh-Bénard convection in a Newtonian liquid is studied in this paper. This consideration is made to capture the possible effects of two-frequency rotation modulation on stability, that is, the onset of convection and the simultaneous amount of heat transfer in the system. The Venezian approach has been asserted on the linearized Lorenz model to derive the correction Rayleigh number as a function of the two frequencies. The Lorenz model with nonlinearities is evaluated numerically to assess the quantity of heat transfer in the system. The present study states that in comparison with existing studies of no-modulation and singlefrequency rotation modulation, two-frequency rotation modulation yields higher stability bounds and thus diminishes the heat transfer. Heat transfer is found to be enhanced by a pair of coprime integers associated with the harmonics in the system.

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Intensified heat transfer in modulated rotating Rayleigh–Bénard convection

Cited by 15 publications

References 16 publications

Rotating turbulent Rayleigh–Bénard convection subject to harmonically forced flow reversals

Rotating turbulent Rayleigh–Bénard convection subject to harmonically forced flow reversals

On trigonometric cosine, square, sawtooth, and triangular wave‐type rotational modulations on triple‐diffusive convection in salted water

The onset of Rayleigh–Bénard convection and heat transfer under two‐frequency rotation modulation

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