Apparatus for the study of Rayleigh–Bénard convection in gases under pressure

Bruyn, John R. de; Bodenschatz, Eberhard; Morris, Stephen W.; Trainoff, Steven P.; Hu, Yuchou; Cannell, David S.; Ahlers, Guenter

doi:10.1063/1.1147511

Cited by 147 publications

(172 citation statements)

References 149 publications

(328 reference statements)

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“…An alternative promising experimental technique for measuring the intensity, though not the temporal spectrum, of nonequilibrium fluctuations is quantitative shadowgraph analysis [28,[50][51][52][53]. The experimental arrangement is similar to the one depicted in Fig.…”

Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

“…The factorT (q) represents an optical transfer function, which can be derived from the optical arrangement used to produce the shadowgraph pictures; it includes contributions from the response of the CCD detector and the density dependence of the refractive index [50,51,53]. Therefore, applying a two-dimensional Fourier transform to the shadowgraph images, one can deduce the structure factor of the fluid as a function of the wave number q at q ⊥ = 0.…”

Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

“…In practice I 0 (x) is calculated by averaging over many shadowgraph images, so that fluctuations cancel out and the resulting I 0 (x) contains only contributions from nonuniform illumination of the sample. From physical and geometrical optics one can demonstrate that the modulus squared of the two-dimensional Fourier transform of the shadowgraph signal, |i(q)| 2 , after taking an azimuthal average, can be expressed as [50,51,53]:…”

Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

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Fluctuations in fluids in thermal nonequilibrium states below the convective Rayleigh–Bénard instability

Zárate

Sengers

2001

Physica A: Statistical Mechanics and its Applications

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Starting from the linearized fluctuating Boussinesq equations we derive an expression for the structure factor of fluids in stationary convection-free thermal nonequilibrium states, taking into account both gravity and finite-size effects. It is demonstrated how the combined effects of gravity and finite size causes the structure factor to go through a maximum value as a function of the wave number q. The appearance of this maximum is associated with a crossover from a q −4 dependence for larger q to a q 2 dependence for very small q. The relevance of this theoretical result for the interpretation of light scattering and shadowgraph experiments is elucidated. The relationship with studies on various aspects of the problem by other investigators is discussed. The paper thus provides a unified treatment for dealing with fluctuations in fluid layers subjected to a stationary temperature gradient regardless of the sign of the Rayleigh number R, provided that R is smaller than the critical value R c associated with the appearance of Rayleigh-Bénard convection.

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Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

Section: Nonequilibrium Structure Factor Probed In Experimentsmentioning

confidence: 99%

See 1 more Smart Citation

Fluctuations in fluids in thermal nonequilibrium states below the convective Rayleigh–Bénard instability

Zárate

Sengers

2001

Physica A: Statistical Mechanics and its Applications

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“…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.…”

mentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

Localized Transverse Bursts in Inclined Layer Convection

2003

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We investigate a novel bursting state in inclined layer thermal convection in which convection rolls exhibit intermittent, localized, transverse bursts. With increasing temperature difference, the bursts increase in duration and number while exhibiting a characteristic wavenumber, magnitude, and size. We propose a mechanism which describes the duration of the observed bursting intervals and compare our results to bursting processes in other systems. PACS numbers: 47.54.+r, Bursting phenomena are a common feature of nonequilibrium systems. Various bursting mechanisms have been described by Knobloch and Moehlis [1] and characterized in terms of their recurrence properties and dynamic range, distinguishing between temporally localized bursts which are spatially global and those which are spatially local. Some examples of the former are the breakdown of spiral vortices in Taylor-Couette flow [2,3], fluctuations in heat transport in binary fluid convection [4,5], and shear flow turbulence [6,7]. While a dynamical systems approach has been fruitful in the global case, spatially localized bursts remain less understood.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. 1). Temporally, we observe multiple cycles of transverse modulation, turbulence, and decay within the bursts. Existing theory does not address either the spatial or temporal dynamics.Inclined layer convection is a variant of Rayleigh-Bénard (thermal) convection [10], in which a fluid layer is heated from one side and and cooled from the other. Tilting this layer by an angle θ (see Fig. 2) results in a base state which is a superposition of a linear temperature gradient and a shear flow up along the hot plate and down along the cold. When heated beyond a critical temperature difference ∆T c , the fluid convects due to the buoyancy of the hot fluid. As θ is increased, the buoyancy provided by the perpendicular component of gravity g ⊥ ≡ g cos θ becomes weaker and the shear flow provided by g becomes stronger. 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. Our three convection cells were of height d = 778 ± 2µm and length 97.3d. The widths in thex direction are L 1 = 10.4d for Cell 1, L 2 = 20.9d for Cell 2, and L 3 = 31.0d for Cell 3. These parameters give a vertical viscous diffusion time of...

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High‐Rate Printing of Micro/Nanoscale Patterns Using Interfacial Convective Assembly

et al. 2020

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Electric-field-directed assembly [31,32] uses electrophoretic and dielectrophoretic forces to direct nanoelements. Although electric-field-directed assembly demonstrates high throughput, high scalability, and high resolution in assembling various nanomaterials, conductive substrates are required to generate electric field, which limits potential applications of printed structures in electronic devices. Fluidicflow-directed assembly such as convective [33][34][35] and capillary [36][37][38] assembly utilizes solvent evaporation-induced convective flow to guide and position nanoelements. Unlike electric-field-directed assembly, fluidic-flow-directed assembly is applicable to all kinds of substrates (both insulating and conductive). However, it takes hours to assemble over centimetersized substrates. Therefore, the scalability and throughput of this assembly process is a major challenge. Photothermally directed assembly uses photothermaleffect-induced Rayleigh-Benard [39] and/or Marangoni [40][41][42] convective flow to direct assembly. Similar to fluidic-flow-directed assembly, photothermally directed assembly suffers from scalability and throughput issues due to its serial processing nature. In addition, photothermally directed assembly has a limited resolution of micro or sub-micro scale. [43,44] Therefore, the development of a broadly applicable, highly scalable, high throughput, and high resolution printing technique is highly desirable.Here, we report a novel fluidic-flow-directed assembly technique, interfacial convective assembly, to rapidly assemble particles in pattern areas on any substrates. In the interfacial convective assembly, a patterned substrate is initially sonicated in isopropyl alcohol (IPA) using a bath type sonicator for a few seconds. With a low surface tension, IPA helps wet as well as remove trapped air in the patterned structures. After sonication, the substrate is removed from the IPA bath, leaving a thin IPA film on the substrate. Afterward, 50 µL aqueous particle suspension is drop casted on the IPA film. The particle suspension immediately mixes with the IPA film, resulting a suspension with ≈20 wt% IPA. Then, a glass slide is covered on the suspension, creating a confined environment with the substrate via a 300 µm thick spacer (Figure 1a). Finally, the setup is placed onto a hot plate with preheated temperatures between 40 and 75 °C. The substrate is heated up, inducing a convective flow. Due to the convective flow, particles are carried toward Printing of electronics has been receiving increasing attention from academia and industry over the recent years. However, commonly used printing techniques have limited resolution of micro-or sub-microscale. Here, a directed-assembly-based printing technique, interfacial convective assembly, is reported, which utilizes a substrate-heating-induced solutal Marangoni convective flow to drive particles toward patterned substrates and then uses van der Waals interactions as well as geometrical confinement to trap the particles in the pattern area...

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Apparatus for the study of Rayleigh–Bénard convection in gases under pressure

Cited by 147 publications

References 149 publications

Fluctuations in fluids in thermal nonequilibrium states below the convective Rayleigh–Bénard instability

Fluctuations in fluids in thermal nonequilibrium states below the convective Rayleigh–Bénard instability

Localized Transverse Bursts in Inclined Layer Convection

High‐Rate Printing of Micro/Nanoscale Patterns Using Interfacial Convective Assembly

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