scholarly journals The Relative Contribution of Solutal Marangoni Convection to Thermal Marangoni Flow Instabilities in a Liquid Bridge of Smaller Aspect Ratios under Zero Gravity

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 116
Author(s):  
Radeesha Laknath Agampodi Mendis ◽  
Atsushi Sekimoto ◽  
Yasunori Okano ◽  
Hisashi Minakuchi ◽  
Sadik Dost
Keyword(s):  
Liquid Bridge ◽  
Marangoni Number ◽  
Marangoni Convection ◽  
Wave Mode ◽  
Dynamic Mode Decomposition ◽  
Flow Instabilities ◽  
Dynamic Mode ◽  
Zone Model ◽  
Zero Gravity ◽  
Aspect Ratios

The effect of solutal Marangoni convection on flow instabilities in the presence of thermal Marangoni convection in a Si-Ge liquid bridge with different aspect ratios As has been investigated by three-dimensional (3D) numerical simulations under zero gravity. We consider a half-zone model of a liquid bridge between a cold (top plane) and a hot (bottom plane) disks. The highest Si concentration is on the top of the liquid bridge. The aspect ratio (As) drastically affects the critical Marangoni numbers: the critical solutal Marangoni number (under small thermal Marangoni numbers (MaTAs≲1800)) has the same dependence on As as the critical thermal Marangoni number (under small solutal Marangoni numbers (400≲MaCAs≲800)), i.e., it decreases with increasing As. The azimuthal wavenumber of the traveling wave mode increases as decreasing As, i.e., larger azimuthal wavenumbers (m=6,7,11,12, and 13) appear for As=0.25, and only m=2 appears when As is one and larger. The oscillatory modes of the hydro waves have been extracted as the spatiotemporal structures by using dynamic mode decomposition (DMD). The present study suggests a proper parameter region of quiescent steady flow suitable for crystal growth for smaller aspect ratios of the liquid bridge.

scholarly journals A Numerical Study on the Exact Onset of Flow Instabilities in Thermo-Solutal Marangoni Convection Driven by Opposing Forces in a Half-Zone Liquid Bridge under Zero Gravity

2021 ◽  
Vol 54 (8) ◽  
pp. 424-430
Author(s):  
Radeesha Laknath ◽  
Agampodi Mendis ◽  
Atsushi Sekimoto ◽  
Yasunori Okano ◽  
Hisashi Minakuchi ◽  
...  
Keyword(s):  
Liquid Bridge ◽  
Marangoni Convection ◽  
Numerical Study ◽  
Flow Instabilities ◽  
Zero Gravity

Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection

2021 ◽  
Author(s):  
Susanne Horn ◽  
Peter J. Schmid ◽  
Jonathan M. Aurnou
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Mean Flow ◽  
Large Scale Circulation ◽  
Convective Systems ◽  
Aspect Ratios ◽  
Mode Decomposition ◽  
Coherent Flow Structure

Abstract The large-scale circulation (LSC) is the most fundamental turbulent coherent flow structure in Rayleigh-B\'enard convection. Further, LSCs provide the foundation upon which superstructures, the largest observable features in convective systems, are formed. In confined cylindrical geometries with diameter-to-height aspect ratios of Γ ≅ 1, LSC dynamics are known to be governed by a quasi-two-dimensional, coupled horizontal sloshing and torsional (ST) oscillatory mode. In contrast, in Γ ≥ √2 cylinders, a three-dimensional jump rope vortex (JRV) motion dominates the LSC dynamics. Here, we use dynamic mode decomposition (DMD) on direct numerical simulation data of liquid metal to show that both types of modes co-exist in Γ = 1 and Γ = 2 cylinders but with opposite dynamical importance. Furthermore, with this analysis, we demonstrate that ST oscillations originate from a tilted elliptical mean flow superposed with a symmetric higher order mode, which is connected to the four rolls in the plane perpendicular to the LSC in Γ = 1 tanks.

Numerical Simulation of Oscillatory Marangoni Flow in Encapsulated Liquid Bridge

2005 ◽  
Author(s):  
Lan Peng ◽  
You-Rong Li ◽  
Nobuyuki Imaishi ◽  
Dan-Ling Zeng ◽  
Qing-Hua Chen
Keyword(s):  
Liquid Bridge ◽  
Marangoni Number ◽  
Oscillatory Flow ◽  
Marangoni Convection ◽  
Silicone Oil ◽  
Temperature Fields ◽  
Critical Conditions ◽  
Simulation Results ◽  
Physical And Mathematical Models ◽  
Oscillation Frequencies

The physical and mathematical models of the Marangoni convection of KF-96 silicone oil and FC-70 fluorinart in an encapsulated liquid bridge were established. To contrast to this configuration, the Marangoni convection of KF-96 silicone oil in a liquid bridge was also studied in present work. We conducted a series of unsteady two-dimensional numerical simulations. Simulation conditions correspond to those in the experiments of Majima and Kawamura (2001). The simulation results with large Marangoni number (Ma) predicted oscillatory flows under microgravity. The critical conditions for the onset oscillatory flow were determined and compared with the experimental results. Details of the flow and temperature fields were discussed. Oscillation frequencies were also exhibited.

Prograde, retrograde, and oscillatory modes in rotating Rayleigh–Bénard convection

2017 ◽  
Vol 831 ◽  
pp. 182-211 ◽  
Author(s):  
Susanne Horn ◽  
Peter J. Schmid
Keyword(s):  
Low Frequency ◽  
Linear Stability Theory ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Aspect Ratios ◽  
Bénard Convection ◽  
Mode Decomposition ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Rotating Rayleigh–Bénard convection is typified by a variety of regimes with very distinct flow morphologies that originate from several instability mechanisms. Here we present results from direct numerical simulations of three representative set-ups: first, a fluid with Prandtl number $Pr=6.4$, corresponding to water, in a cylinder with a diameter-to-height aspect ratio of $\unicode[STIX]{x1D6E4}=2$; second, a fluid with $Pr=0.8$, corresponding to $\text{SF}_{6}$ or air, confined in a slender cylinder with $\unicode[STIX]{x1D6E4}=0.5$; and third, the main focus of this paper, a fluid with $Pr=0.025$, corresponding to a liquid metal, in a cylinder with $\unicode[STIX]{x1D6E4}=1.87$. The obtained flow fields are analysed using the sparsity-promoting variant of the dynamic mode decomposition (DMD). By means of this technique, we extract the coherent structures that govern the dynamics of the flow, as well as their associated frequencies. In addition, we follow the temporal evolution of single modes and present a criterion to identify their direction of travel, i.e. whether they are precessing prograde or retrograde. We show that for moderate $Pr$ a few dynamic modes suffice to accurately describe the flow. For large aspect ratios, these are wall-localised waves that travel retrograde along the periphery of the cylinder. Their DMD frequencies agree with the predictions of linear stability theory. With increasing Rayleigh number $Ra$, the interior gradually fills with columnar vortices, and eventually a regular pattern of convective Taylor columns prevails. For small aspect ratios and close enough to onset, the dominant flow structures are body modes that can precess either prograde or retrograde. For $Pr=0.8$, DMD additionally unveiled the existence of so far unobserved low-amplitude oscillatory modes. Furthermore, we elucidate the multi-modal character of oscillatory convection in low-$Pr$ fluids. Generally, more dynamic modes must be retained to accurately approximate the flow. Close to onset, the flow is purely oscillatory and the DMD reveals that these high-frequency modes are a superposition of oscillatory columns and cylinder-scale inertial waves. We find that there are coexisting prograde and retrograde modes, as well as quasi-axisymmetric torsional modes. For higher $Ra$, the flow also becomes unstable to wall modes. These low-frequency modes can both coexist with the oscillatory modes, and also couple to them. However, the typical flow feature of rotating convection at moderate $Pr$, the quasi-steady Taylor vortices, is entirely absent in low-$Pr$ flows.

Transient Marangoni convection induced by an isothermal sidewall of a rectangular liquid pool

2021 ◽  
Vol 928 ◽  
Author(s):  
Enhui Chen ◽  
Feng Xu
Keyword(s):  
Marangoni Number ◽  
Scaling Laws ◽  
Marangoni Convection ◽  
Liquid Pool ◽  
Surface Flow ◽  
Scaling Analysis ◽  
Zero Gravity ◽  
Vertical Flow ◽  
Gravity Condition ◽  
Good Agreement

Transient Marangoni convection induced by an isothermal sidewall of a rectangular pool under a zero-gravity condition is studied using scaling analysis. Scaling analysis shows that there exist a number of flow regimes in each evolution scenario, depending on the Marangoni number, the Prandtl number and the aspect ratio. In a typical evolution scenario, a horizontal surface flow and a vertical flow adjacent to the sidewall may appear. Additionally, a number of scaling laws of the velocity and thickness of transient Marangoni convection are obtained. Further, numerical simulation is performed for validation of the selected scaling laws. There exits good agreement between the numerical results and the scaling predictions.

Global Linear Stability Analysis of Thermo-solutal Marangoni Convection in a Liquid Bridge Under Zero Gravity

2020 ◽  
Vol 32 (4) ◽  
pp. 729-735
Author(s):  
Radeesha Laknath Agampodi Mendis ◽  
Atsushi Sekimoto ◽  
Yasunori Okano ◽  
Hisashi Minakuchi ◽  
Sadik Dost
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Liquid Bridge ◽  
Marangoni Convection ◽  
Zero Gravity

scholarly journals Dynamic Mode Decomposition of Elliptical Liquid Jets in Crossflow

2021 ◽  
Author(s):  
Keivan Mokhtarpour ◽  
Mehdi Jadidi ◽  
Ali Dolatabadi
Keyword(s):  
High Speed ◽  
Flux Ratio ◽  
Open Loop ◽  
Dynamic Mode Decomposition ◽  
Liquid Jets ◽  
Dynamic Mode ◽  
Equivalent Diameter ◽  
Arnoldi Method ◽  
Aspect Ratios ◽  
Mode Decomposition

Dynamics of round and elliptical liquid jets in subsonic crossflow is studied using high-speed imaging technique. The experiments are performed at constant gaseous weber number and liquid-gas momentum flux ratio of 6.45 and 17.87 respectively, with orifices of different aspect ratios having an equivalent diameter of 0.43 mm. All cases are carried out inside an open loop subsonic wind tunnel with a test section of 100*100*750 mm. For each case, dynamic modes are generated directly from the snapshots using a variant of Arnoldi method known as the dynamic mode decomposition (DMD). DMD results indicate that elliptical liquid jets have more small-scaled patterns with higher frequencies compared to the case of round liquid jets. As the first attempt to investigate the dynamics of elliptical liquid jets in crossflow, present work captures the dominant spatio-temporal structures. It is also found that the orifice aspect ratio can alter the jet wavelengths remarkably. The extracted data of this work can provide beneficial information on the behaviour of elliptical liquid jets exposed to the gas crossflow in the enhanced capillary breakup regime.

Nonlinear Marangoni convection in bounded layers. Part 2. Rectangular cylindrical containers

1982 ◽  
Vol 120 ◽  
pp. 123-138 ◽  
Author(s):  
S. Rosenblat ◽  
G. M. Homsy ◽  
S. H. Davis
Keyword(s):  
Marangoni Number ◽  
Marangoni Convection ◽  
Cell Interaction ◽  
The Other ◽  
Circular Cylinders ◽  
Horizontal Dimension ◽  
Aspect Ratios ◽  
Double Eigenvalues ◽  
Convective State ◽  
Time Periodic

Attention is confined to roll-cell development and roll-cell interaction appropriate to one horizontal dimension larger than either the other horizontal dimension or the depth. At simple eigenvalues Mc the roll-cell amplitude and transport fields can be obtained. Near those aspect ratios corresponding to double eigenvalues Mc, where two roll-cell states of linear theory areequallylikely, thenonlinear theory predicts sequences of transitions from one steady convective state to another as the Marangoni number is increased. Direct comparisons are made of the results here with those of the previous paper for Marangoni convection in circular cylinders. Time-periodic convection is possible in certain cases.

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