Effect of interface deformability on thermocapillary motion of a drop in a tube

S. Mahesri, H. Haj-Hariri, A. Borhan

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The effect of an externally imposed axial temperature gradient on the mobility and deformation of a drop in an otherwise stagnant liquid within an insulated cylindrical tube is investigated. In the absence of bulk transport of momentum and energy, the boundary integral technique is used to obtain the flow and temperature fields inside and outside the deformable drop. The steady drop shapes and the corresponding migration velocities are examined over a wide range of the dimensionless parameters. The steady drop shape is nearly spherical for dimensionless drop sizes <0.5, but becomes slightly elongated in the axial direction for drop sizes comparable to tube diameter. The adverse effect of drop deformation on the effective temperature gradient driving the motion is slightly more pronounced than its favorable effect of reducing drag, thereby leading to a slight reduction in drop mobility with increasing drop deformation. Increasing the viscosity ratio reduces drop deformation and leads to a slight enhancement in the relative mobility (with respect to free thermocapillary motion) of confined drops. When the drop fluid has a lower thermal conductivity than the exterior phase, the presence of the thermally-insulating wall increases the thermal driving force for drop motion (compared to that for the same drop in unbounded domain) by causing more pronounced bending of the isotherms toward the drop. However, the favorable thermal effect of the confining wall is overwhelmed by its retarding hydrodynamic effect, causing the confined drop to always move slower than its unbounded counterpart regardless of the value of the thermal conductivity ratio.

Original languageEnglish (US)
Pages (from-to)363-372
Number of pages10
JournalHeat and Mass Transfer/Waerme- und Stoffuebertragung
Volume50
Issue number3
DOIs
StatePublished - Mar 2014

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Fluid Flow and Transfer Processes

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