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ABSTRACT
The work focuses on developing a detailed understanding of the effects of initial composition (Cin) and bottom cooling temperatures (TB) on different characteristics of double-diffusive convection during unidirectional solidification of water-NH4Cl solution in a complete non-intrusive manner. The qualitative investigation, simultaneous quantification of transported parameters (composition and temperature) and fluid velocities associated with flow patterns are carried out using rainbow schlieren deflectometry, dual-wavelength interferometry and PIV (particle image velocimetry) technique respectively. The dependence of the characteristics of double-diffusive convection for different Cin and TB is explained on the basis of real-time whole-field investigation using a combination of aforementioned imaging techniques.
Nomenclature
| DDL | = | Double-diffusive layer |
| Cin | = | Initial composition (wt.%) |
| TB | = | Bottom cooling temperature (℃) |
| TE | = | Eutectic temperature (℃) |
| L | = | Width of the test cell (mm) |
| = | Height of DDLs (mm) | |
| = | Horizontal thermal gradient (℃/m) | |
| = | Vertical composition gradient (wt.%/m) | |
| = | Coefficient of thermal expansion (K−1) | |
| = | Coefficient of solutal expansion (wt.%−1) | |
| λ | = | Wavelength (m) |
| = | Phase values (rad) | |
| L | = | Path length through the test chamber (m) |
| = | Refractive-index | |
| x, y | = | Coordinate axes |
| αT | = | Thermal diffusivity (m2/s) |
| αS | = | Solutal diffusivity (m2/s) |
| v | = | Kinematic viscosity (m2/s) |
| g | = | Acceleration due to gravity (m/s2) |
| ∆T | = | Lateral temperature difference (℃) |
| ∆C | = | Vertical compositional difference (wt.%) |
| l | = | Length scale (mm) |
| ω | = | Vorticity (1/s) |
| Subscripts | = | |
| 1 | = | Red wavelength |
| 2 | = | Blue wavelength |
| E | = | Eutectic point |
| in | = | Initial point |
| B | = | Bottom surface |
| H | = | Horizontal direction |
| V | = | Vertical direction |
| T | = | Thermal |
| S | = | Solutal |
Acknowledgement
Authors acknowledge the financial support from Department of Science and Technology (DST), India (Grants: EMR/2015/001140, RD/0119-DST0000-007).
Disclosure statement
No potential conflict of interest was reported by the author(s).