Evolution of Flow and Streaming in Exponential Variable Cross-Section Resonators
Round 1
Reviewer 1 Report
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Comments for author File: 
Comments.pdf
Author Response
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Reviewer 2 Report
This is a paper studying the flow field in a resonator of a specific geometry. In my opinion, this work can have some interest for the scientific community. Some comments for the present version of the paper include:
The boundary condition on the moving boundary and the connection with the rest of the formulation is not clear to me. A more extended description is required. Some papers for oscilatory flows following a different approach, but based on gas kinetic schemes could be of some interest and might be included in the reference list. Some of them are: A. Tsimpoukis and D. Valougeorgis, Pulsatile pressure driven rarefied gas flow in long rectangular ducts, Physics of Fluids, 30, 047104, 2018. D. Kalempa and F. Sharipov, Sound propagation through a rarefied gas confined between source and receptor at arbitrary Knudsen number and source frequency, Physics of Fluids, 21, 103601, 2009. References in these papers. It is well known that BGK model results to a Prandtl number equal to 1. Since in this work air is the working fluid, the Prandtl number is not correct and the results concerning temperature can not be considered as reliable. So this is something that has to be treated, either by removing some of the results and commenting on it, or by explaining why this results can be considered valid. Some typos have to be corrected (for example line 122).Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The resonator is axisymmetric. This explains the display of one half of its cross-section in Figs. 8, 9, and 11. At the same time, Fig. 10 shows the entire cross-section. Here, one can see that the flow field distributions are not axisymmetric, especially those shown in Figs. 10c and 10g. From the physical point of view, it is not clear why the symmetry must be broken. May be it is better to consider such an approach to grid generation, in which it will be symmetric with respect to the axis of the resonator.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The reviewer appreciate the effort to improve the manuscript.
Now the paper can be accepted for publication.
I am sorry to hear the situation on coronavirus in China. I hope that everything will be fine soon. The flow vectors are really hard to see, so I appreciate if you could revise the color of vectors in the final editing process.
