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פותח על ידי קלירמאש פתרונות בע"מ -
Effects of Interaction Between Marangoni and Double-Diffusive Instabilities
Year:
1995
Source of publication :
Journal of Fluid Mechanics
Authors :
טנאי, יוסף
;
.
Volume :
303
Co-Authors:
Tanny, J., Center for Technological Education Holon, POB 305, Holon, 58102, Israel, Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ, 85721, United States
Chen, C.F., Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ, 85721, United States
Facilitators :
From page:
1
To page:
21
(
Total pages:
21
)
Abstract:
The effect of surface tension on the onset of convection in a horizontal double-diffusive layer was studied both experimentally and by linear stability analysis. The experiments were conducted in a rectangular tank with base dimension of 25 x 13 cm and 5 cm in height. A stable solute (NaCl) stratification was first established in the tank, and then a vertical temperature gradient was imposed. Vertical temperature and concentration profiles were measured using a thermocouple and a conductivity probe and the flow patterns were visualized by a schlieren system. Two types of experiments were carried out which illustrate the effect of surface tension on the onset of convection. In the rigid-rigid experiments, when the critical thermal Rayleigh number, RT, is reached, large double-diffusive plumes were seen simultaneously to rise from the heated bottom and descend from the cooled top. In the rigid-free experiments, owing to surface-tension effects, the first instability onset was of the Marangoni type. Well-organized small plumes were seen to emerge and persist close to the top free surface at a relatively small RMT (where subscript M denotes ‘Marangoni’). At larger RbT > RtT (where subscript t denotes ‘top’) these plumes evolved into larger double-diffusive plumes. The onset of double-diffusive instability at the bottom region occurred at a still higher RbT > RtT (where subscript b denotes ‘bottom’), A series of stability experiments was conducted for a layer with an initial top concentration of 2wt% and different concentration gradients. The stability map shows that in the rigid-free case the early Marangoni instability in the top region reduces significantly the critical RT for the onset of double-diffusive convection. Compared with the rigid-rigid case, the critical RT in the top region is reduced by about 60 % and in the bottom region by about 30%. The results of the linear stability analysis, which takes into account both surface-tension and double-diffusive effects, are in general agreement with the experiments. The analysis is then applied to study the stability characteristics of such a layer as gravity is reduced to microgravity level. Results show that even at 10-4go, where g0is the gravity at sea level, the double-diffusive effect is of equal importance to the Marangoni effect. © 1995, Cambridge University Press. All rights reserved.
Note:
Related Files :
Flow interactions
Flow patterns
Heat convection
Marangoni instability
Schlieren systems
thermal stratification
Vertical temperature
עוד תגיות
תוכן קשור
More details
DOI :
10.1017/S0022112095004150
Article number:
Affiliations:
Database:
סקופוס
Publication Type:
מאמר
;
.
Language:
אנגלית
Editors' remarks:
ID:
28046
Last updated date:
02/03/2022 17:27
Creation date:
17/04/2018 00:36
Scientific Publication
Effects of Interaction Between Marangoni and Double-Diffusive Instabilities
303
Tanny, J., Center for Technological Education Holon, POB 305, Holon, 58102, Israel, Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ, 85721, United States
Chen, C.F., Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ, 85721, United States
Effects of Interaction Between Marangoni and Double-Diffusive Instabilities
The effect of surface tension on the onset of convection in a horizontal double-diffusive layer was studied both experimentally and by linear stability analysis. The experiments were conducted in a rectangular tank with base dimension of 25 x 13 cm and 5 cm in height. A stable solute (NaCl) stratification was first established in the tank, and then a vertical temperature gradient was imposed. Vertical temperature and concentration profiles were measured using a thermocouple and a conductivity probe and the flow patterns were visualized by a schlieren system. Two types of experiments were carried out which illustrate the effect of surface tension on the onset of convection. In the rigid-rigid experiments, when the critical thermal Rayleigh number, RT, is reached, large double-diffusive plumes were seen simultaneously to rise from the heated bottom and descend from the cooled top. In the rigid-free experiments, owing to surface-tension effects, the first instability onset was of the Marangoni type. Well-organized small plumes were seen to emerge and persist close to the top free surface at a relatively small RMT (where subscript M denotes ‘Marangoni’). At larger RbT > RtT (where subscript t denotes ‘top’) these plumes evolved into larger double-diffusive plumes. The onset of double-diffusive instability at the bottom region occurred at a still higher RbT > RtT (where subscript b denotes ‘bottom’), A series of stability experiments was conducted for a layer with an initial top concentration of 2wt% and different concentration gradients. The stability map shows that in the rigid-free case the early Marangoni instability in the top region reduces significantly the critical RT for the onset of double-diffusive convection. Compared with the rigid-rigid case, the critical RT in the top region is reduced by about 60 % and in the bottom region by about 30%. The results of the linear stability analysis, which takes into account both surface-tension and double-diffusive effects, are in general agreement with the experiments. The analysis is then applied to study the stability characteristics of such a layer as gravity is reduced to microgravity level. Results show that even at 10-4go, where g0is the gravity at sea level, the double-diffusive effect is of equal importance to the Marangoni effect. © 1995, Cambridge University Press. All rights reserved.
Scientific Publication
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