Experimental study of the global flow-state transformation in a rectangular Rayleigh-Bénard sample

Horstmann, Gerrit Maik; Schiepel, Daniel; Wagner, Claus

doi:10.1016/j.ijheatmasstransfer.2018.05.097

Cited by 8 publications

(9 citation statements)

References 32 publications

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“…However, our results are not consistent with the experimental results of Horstmann et al. (2018), who found in a cell of lateral aspect ratio that the amplitudes of the first two modes do not have a strong dependence in the range of our experiments; the reason for this inconsistency is not known to us. It is found that is very close to the transitional between ASRS and SRS; thus from now on we will not distinguish between the former and the latter.…”

Section: Resultscontrasting

confidence: 99%

“…In the (quasi-) 2-D geometry, corner rolls were found to play a crucial role in the reversal process: they grow in size to weaken and eventually break up the main circulating roll, and then merge to form a new single roll again, but with a reversed circulating direction (Sugiyama et al 2010;Chandra & Verma 2013). The role of the corner rolls in LSC reversal was further delineated by a number of subsequent experimental and numerical studies (Ni et al 2015;Podvin & Sergent 2015;Huang & Xia 2016;Horstmann, Schiepel & Wagner 2018;Wang et al 2018a). However, a recent experimental work by Wang et al (2018b) found that reversals of the LSC also occurred in a thin circular cell.…”

Section: Introductionmentioning

confidence: 96%

“…The role of the corner rolls in LSC reversal was further delineated by a number of subsequent experimental and numerical studies (Ni et al. 2015; Podvin & Sergent 2015; Huang & Xia 2016; Horstmann, Schiepel & Wagner 2018; Wang et al. 2018 a ).…”

Section: Introductionmentioning

confidence: 97%

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Emergence of substructures inside the large-scale circulation induces transition in flow reversals in turbulent thermal convection

et al. 2019

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We present an experimental study of the reversal of the large-scale circulation (LSC) in quasi-two-dimensional turbulent Rayleigh–Bénard convection. It is found that there exists a transition in the Rayleigh number ($Ra$) dependence of the reversal rate $f$ with two distinct scalings: for $Ra$ less than a transitional value $Ra_{t}$, the non-dimensionalized reversal rate $ft_{E}\sim Ra^{-1.09}$; however, for higher $Ra$ the scaling changes to $ft_{E}\sim Ra^{-3.06}$, where $t_{E}$ is the turnover time of the LSC. Flow visualization shows that this regime transition originates from a change in flow topology from a single-roll state to a new, less stable, abnormal single-roll state with substructures inside the single roll. The emergence of the substructures inside the LSC lowers the energy barrier for the flow reversals to occur and leads to a slower decay of $f$ with $Ra$. Detailed analysis reveals that, although it is the corner rolls that trigger the reversal event, the probability for the occurrence of reversals mainly depends on the stability of the LSC. This is supported by a model we proposed to predict the critical condition for the transition, which agrees well with the experimental results.

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Section: Resultscontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Emergence of substructures inside the large-scale circulation induces transition in flow reversals in turbulent thermal convection

et al. 2019

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“…In the case of such powers as the USA exploration of the intellectual strength of Asian and European countries is also significant. (Horstmann et al, 2018) Already emphasized "brainwashing" and the research and development base typical of North America can not be discounted in the countries of Central and Eastern European countries with any outlays on this form of impact on the reduction of the distance. In convergence models, knowledge-based resources are a new dimension introduced into the Cobb-Douglas model.…”

Section: Endogenous Models In Convergencementioning

confidence: 99%

Socio-Economic Convergence in Models of Endogenous Economic Growth

Szkutnik¹,

Szkutnik²

2018

EMS

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The main results regarding determined goals of the paper concern the analysis of convergence in relation to the convergence processes from the point of view of physical capital and human knowledge, as well as labour resources. They usually refer to Mankiw's model that is a generalisation of the neoclassical Solow model. The major goal of deliberations conducted in the paper can lead to the conclusion that the phenomenon of convergence raises several methodological controversies resulting from inclusion of the very method of GDP per capita estimation, or firstly, the additional Mankiw's variable, i.e. human capital. Various sources, frequently different in the assessment of specific economic indicators prove, that in the countries of significant underdevelopment, the share of human capital followed what was not always positive in other regions of the world. The paper indicates the emergence of knowledge capital that is an empirically weakly defined variable, yet vital in convergence analyses. The measurements of knowledge capital applied in various models are usually not the same or reliable, which causes poor identification of the model, and the lack of possibility to compare obtained results. This leads to a distortion of the model of evaluation of the level of cohesion in compared economies. It results from the fact that such resources as human capital are not directly observable. The paper presents other possible ways of measuring the knowledge capital proposed in the literature, and it especially indicates that it requires the adoption of additional restrictive assumptions. In particular, it is assumed that the pace of technological progress is constant over time and between countries. The paper also evaluates the chances of convergence of countries with a lower degree of economic and social development, while taking into account the economic context.

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“…Three-dimensional flow field measurement techniques have been developed for obtaining massive volumetric data sets for high temporal and spatial resolution from high-speed and multiple cameras while simultaneously reducing computation time and increasing reliability [1-3]. Among various three-dimensional flow field measurement techniques, it is known that particle tracking velocimetry (PTV) is able to obtain more complicated trajectories of particles and velocity vectors, for instance three-dimensional Reyleigh-Benard convection flow of the laminar-turbulent transition regime [4], three-dimensional vertical flow structures in a submerged hydraulic jump [5], and free-stream flow of the trisonic wind tunnel [6].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional particle tracking velocimetry using shallow neural network for real-time analysis

et al. 2020

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Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX Three-dimensional particle tracking velocimetry (3D-PTV) technique is widely used to acquire the complicated trajectories of particles and flow fields. It is known that the accuracy of 3D-PTV depends on the mapping function to reconstruct three-dimensional particles locations. The mapping function becomes more complicated if the number of cameras is increased and there is a liquid-vapor interface, which crucially affect the total computation time. In this paper, using a shallow neural network model (SNN), we dramatically decrease the computation time with a high accuracy to successfully reconstruct the three-dimensional particle positions, which can be used for real-time particle detection for 3D-PTV. The developed technique is verified by numerical simulations and applied to measure a complex solutal Marangoni flow patterns inside a binary mixture droplet.

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Experimental study of the global flow-state transformation in a rectangular Rayleigh-Bénard sample

Cited by 8 publications

References 32 publications

Emergence of substructures inside the large-scale circulation induces transition in flow reversals in turbulent thermal convection

Emergence of substructures inside the large-scale circulation induces transition in flow reversals in turbulent thermal convection

Socio-Economic Convergence in Models of Endogenous Economic Growth

Three-dimensional particle tracking velocimetry using shallow neural network for real-time analysis

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