EXTENDED SELF-SIMILARITY AND THE MOST INTENSE VELOCITY STRUCTURES IN TURBULENT RAYLEIGH–BÉNARD CONVECTION

2003 ◽  
Vol 17 (04) ◽  
pp. 131-139 ◽  
Author(s):  
EMILY S. C. CHING ◽  
T. P. CHOY ◽  
K. W. CHUI
Keyword(s):  
Turbulent Flows ◽  
Maximum Velocity ◽  
Velocity Measurements ◽  
Self Similarity ◽  
Extended Self ◽  
Velocity Difference ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

It has been conjectured13 that the extended self-similarity measured in turbulent flows is an indication of the maximum velocity difference being scale-independent and thus the most intense velocity structures being shock-like. In this paper, we present analyses of velocity measurements in turbulent Rayleigh–Bénard convection that show further support to this conjecture.

scholarly journals Temperature profiles measurements in turbulent Rayleigh-Bénard convection by optical fibre system at the Barrel of II-menau

2018 ◽  
Vol 180 ◽  
pp. 02020
Author(s):  
Jakub Drahotský ◽  
Pavel Hanzelka ◽  
Věra Musilová ◽  
Michal Macek ◽  
Ronald du Puits ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Optical Fibre ◽  
Large Scale ◽  
Temperature Profiles ◽  
Vertical Temperature ◽  
Thin Glass ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Modelling of large-scale natural (thermally-generated) turbulent flows (such as the turbulent convection in Earth’s atmosphere, oceans, or Sun) is approached in laboratory experiments in the simplified model system called the Rayleigh-Bénard convection (RBC). We present preliminary measurements of vertical temperature profiles in the cell with the height of 4:7 m, 7:15m in diameter, obtained at the Barrel of Ilmenau (BOI), the worldwide largest experimental setup to study highly turbulent RBC, newly equipped with the Luna ODiSI-B optical fibre system. In our configuration, the system permits to measure the temperature with a high spatial resolution of 5mm along a very thin glass optical fibre with the length of 5m and seems to be perfectly suited for measurement of time series of instantaneous vertical temperature profiles. The system was supplemented with the two Pt100 vertically movable probes specially designed by us for reference temperature profiles measurements.

Experimental study of the velocity field in Rayleigh-Bénard convection

1978 ◽  
Vol 85 (4) ◽  
pp. 641-653 ◽  
Author(s):  
M. Dubois ◽  
P. Bergé
Keyword(s):  
Experimental Study ◽  
Velocity Field ◽  
Local Velocity ◽  
Velocity Measurements ◽  
Bénard Convection ◽  
Benard Convection ◽  
Theoretical Predictions ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Velocity Mode

Local velocity measurements performed in a convecting layer of fluid show that the velocity field can be described by a dominant fundamental velocity mode mixed with an increasing proportion of second and third harmonics as ε, the reduced distance to the convective thresholdRc, is increased from 0 to ∼ 10. The spatial and thermal dependences of the amplitudes of these different modes are reported and compared with theoretical predictions.

scholarly journals Data-driven reduced modelling of turbulent Rayleigh–Bénard convection using DMD-enhanced fluctuation–dissipation theorem

2018 ◽  
Vol 852 ◽  
Author(s):  
M. A. Khodkar ◽  
Pedram Hassanzadeh
Keyword(s):  
Turbulent Flows ◽  
Data Driven ◽  
High Dimensional ◽  
Dynamic Mode ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

A data-driven model-free framework is introduced for the calculation of reduced-order models (ROMs) capable of accurately predicting time-mean responses to external forcings, or forcings needed for specified responses, e.g. for control, in fully turbulent flows. The framework is based on using the fluctuation–dissipation theorem (FDT) in the space of a limited number of modes obtained from dynamic mode decomposition (DMD). Use of the DMD modes as the basis functions, rather than the commonly used proper orthogonal decomposition modes, resolves a previously identified problem in applying FDT to high-dimensional non-normal turbulent flows. Employing this DMD-enhanced FDT method ($\text{FDT}_{DMD}$), a linear ROM with horizontally averaged temperature as state vector is calculated for a 3D Rayleigh–Bénard convection system at a Rayleigh number of$10^{6}$using data obtained from direct numerical simulation. The calculated ROM performs well in various tests for this turbulent flow, suggesting$\text{FDT}_{DMD}$as a promising method for developing ROMs for high-dimensional turbulent systems.

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