Heat and momentum transport scalings in horizontal convection

Shishkina, Olga; Großmann, Siegfried; Lohse, Detlef

doi:10.1002/2015gl067003

Cited by 63 publications

(81 citation statements)

References 51 publications

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“…Hignett et al [17] developed a theoretical framework for deriving this scaling law for the heat transfer in an annulus with a differentially heated base and found α = 1/5. An exponent of 1/5 is also given by the Rossby scaling for non-rotating horizontal convection [27], although the universality of this law has been questioned [28]. Hignett et al's [17] analysis has since been applied to an internally heated annulus [16] and the classical configuration [14] to give α = 1/4, which is in agreement with experiment.…”

Section: Introductionmentioning

confidence: 70%

“…Over a large Rayleigh number range, the heat transport was found overall to be well described by a phenomenological model proposed by Grossmann and Lohse (the GL model) [33][34][35][36][37][38] based on an assumption of low Reynolds number and laminar boundary layers. More recently the approach has also been applied to horizontal convection [28,39]. The model proposes that there is no universal scaling law for the Nusselt number but that α is dependent on the region of Rayleigh/Prandtl number space in which the experiment takes place (see [28] Figure 2).…”

Section: Introductionmentioning

confidence: 99%

“…More recently the approach has also been applied to horizontal convection [28,39]. The model proposes that there is no universal scaling law for the Nusselt number but that α is dependent on the region of Rayleigh/Prandtl number space in which the experiment takes place (see [28] Figure 2). In the new annulus the heat source and sink are displaced both vertically and horizontally from each other.…”

Section: Introductionmentioning

confidence: 99%

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Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

Wright

Scolan

et al. 2017

Fluids

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Abstract:We present a numerical study of axisymmetric flow in a rotating annulus in which local thermal forcing, via a heated annular ring on the outside of the base and a cooled circular disk in the centre of the top surface, drives convection. This new configuration is a variant of the classical thermally-driven annulus, where uniform heating and cooling are applied through the outer and inner sidewalls respectively. The annulus provides an analogue to a planetary circulation and the new configuration, with its more relaxed vertical thermal boundary conditions, is expected to better emulate vigorous convection in the tropics and polar regions as well as baroclinic instability in the mid-latitude baroclinic zone. Using the Met Office/Oxford Rotating Annulus Laboratory (MORALS) code, we have investigated a series of equilibrated, two dimensional axisymmetric flows across a large region of parameter space. These are characterized in terms of their velocity and temperature fields. When rotation is applied several distinct flow regimes may be identified for different rotation rates and strengths of differential heating. These regimes are defined as a function of the ratio of the horizontal Ekman layer thickness to the non-rotating thermal boundary layer thickness and are found to be similar to those identified in previous annulus experiments. Convection without rotation is also considered and the scaling of the heat transport with Rayleigh number is calculated. This is then compared with existing work on the classical annulus as well as horizontal and Rayleigh-Bénard convection. As with previous studies on both rotating and non-rotating convection the system's behaviour is found to be aspect ratio dependent. This dependence is seen in the scaling of the non-rotating Nusselt number and in transitions between regimes in the rotating case although further investigation is required to fully explain these observations.

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Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

Wright

Scolan

et al. 2017

Fluids

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“…This little tilting hardly affects Nu [38]; here we find an effect of less than 2% in all cases, much less than through roughness or the orientation of the roughness. The aim of the tilting is to lock the LSCR direction as sketched in Figs.…”

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confidence: 74%

Controlling Heat Transport and Flow Structures in Thermal Turbulence Using Ratchet Surfaces

et al. 2018

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In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchet-like roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the Large Scale Circulation Roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through a quantitative analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. The current work has important implications for passive and active flow control in engineering, bio-fluid dynamics, and geophysical flows.Turbulent convective flows over rough surfaces are ubiquitous in engineering and geophysical flows. Examples include convective flows in the atmosphere and in oceans, where the ground, sea-bed and ocean floor are generally not smooth. As the ability to enhance convective heat transfer is crucial in many industrial applications, numerous strategies have been proposed to efficiently enhance it. Among several approaches, introducing wall roughness is an effective way to do so. Indeed, the study of surface roughness effects in wall-bounded turbulent flows has been an area of intense research (see e.g. some recent work [1][2][3][4][5][6][7][8], the reviews [9,10], and the textbooks [11,12]). Similarly, several studies have been conducted on turbulent thermal convection over rough plates [13][14][15][16][17][18][19][20]. The vast majority of these studies with rough walls adopt some ordered and symmetrical structures, such as pyramids, squares, rectangles etc. However, the rough surfaces in engineering applications and in nature are in general not symmetric, resulting in complex interactions between the flow and the asymmetric roughness elements. Examples are wind blowing over a landscape with asymmetric slopes and ocean flows over an asymmetric sea-bed, etc. Other examples include marine animals which can actively change the asymmetric roughness for maneuverability.In this work, we aim to study the influences of ratchetlike wall structures on the flow organization and heat transfer in fully developed convective thermal turbulence. Indeed, building on the classical Feynman-Smoluchowski ratchet, in various contexts researchers have proposed ratchet-type mechanisms and devices that operate outside of thermal equilibrium [21]. Examples include the so-called 'capillary-ratchet' in zoology [22], a rotational ratchet in a granular gas [23], self-propelled Leidenfrost droplets and solids on ratchet sur...

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“…[10]). Since we are interested in turbulence dominated regimes where the scaling is not determines by the buoyancy forcing profile, nor the aspect ratio [16,15], nor the ype of boundary condition, free-slip boundary conditions are used for the velocity on the upper, lower and end walls at x = ±L/2 (see ref. [14]) while the domain is assumed periodic in the transverse direction y.…”

mentioning

confidence: 99%

Poster: Turbulent Horizontal Convection at High Prandtl Numbers

Passaggia¹,

Hurley²,

White³

et al. 2016

69th Annual Meeting of the APS Division of Fluid Dynamics - Gallery of Fluid Motion

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NaCl identified by adding NaHSo 4 (pH reducer) for LIF RhodamineWT (pH insensitive) / Fluorescein (pH sensitive) Band-pass filter at 530 nm ( Fluorescein) Band-pass filter at 580 nm (Rhodamine)The spatio-temporal diagnosis of the density of non homogeneous salt water is a difficult task, largely because the diffusion coefficient of organic dyes is one order of magnitude lower than the that of salt. Instead of using a single dye we introduce a second dye and a blend of sodium bisulfate with sodium chloride to decrease the pH of the salt water.

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Heat and momentum transport scalings in horizontal convection

Cited by 63 publications

References 51 publications

Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

Controlling Heat Transport and Flow Structures in Thermal Turbulence Using Ratchet Surfaces

Poster: Turbulent Horizontal Convection at High Prandtl Numbers

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