Marangoni Bursting: Insight into the Role of the Thermocapillary Effect in an Oil Bath

Round 1

Reviewer 1 Report

This paper investigated the Marangoni bursting of a droplet of binary mixture on a bath of oil. The authors were especially interested in the final stage of evaporation. They found an inward receding of the circle at the final stage and they argued that the receding was driven by thermocapillary effect in the oil layer. The results are interesting. But the following issues are necessary to answer before this paper will be considered to accept for publication.

1. The authors detected the temperature of the droplet of binary mixture and the oil layer by an IR camera. Although the IR camera was calibrated, the temperature detected by IR camera directly depends on the emissivity of target surface. Due to the different emissivity of the droplet fluids and the oil fluids, their true temperatures should be modified according to their emissivities after detected. Moreover, the emissivity of the droplet depends on the concentration of the binary mixture, which is varied with evaporation. The precision of the temperature measured by authors in this paper is thus questionable.

2. The fluids of the droplet and the oil are transparent or opaque for the infrared light with wavelength between 7.5 to 14 micron? This will also give influence on the measurement of IR camera.  

3. The parameters of the emissivity of the droplet and the oil should be given in the text.  

4. Since the temperature difference of the oil layer was measured, the surface fluid flow velocity of thermal Marangoni flow therefore can be theoretically estimated according to the Marangoni number. By comparing the theoretical result and the experimental result, the thermocapillary flow can be verified by this way.  

Author Response

Please see the attachment pdf file.

Author Response File: Author Response.pdf

Reviewer 2 Report

This authors observe the Marangoni bursting from a new perspective, which means the perspective of temperature changes, and monitor the fragmentation instabilities using thermal camera during the process. Furthermore, they use COMSOL Multiphysics software platform to simulate the Marangoni thermocapillary effect, and the results can support their experimental observations.

Here are some comments and suggestions:

1) The relationship between the peripheric ring radius R and time t when  is given in Fig. 3, and the authors also give the corresponding coefficients. But when  is another number, is the relationship between R and t still suitable? If it isn’t suitable, what is the variation of the relationship between R and t with respect to changes in ?

2) The quality of the images in the manuscript is insufficiently clear. Please provide higher resolution images for better clarity.

3) Some unit format and symbol format in some lines appear to be incorrectly formatted, for example, 416, 486-500.

4) It would be better to provide legends in Fig. 10 to denote the significance of different curves would enhance the reader's comprehension.

Author Response

Please see the attachment file pdf.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have answered the concerns and thus this paper can be accepted as its current form. 

Author Response

Dear Reviewer, 

Thank you for your positive opinion about the revised version of our manuscript.

Many thanks also for your help critical comments to the manuscript that helped us to improve it.

Sincerely yours

Andrzej Miniewicz