Sharp and Rounded Cutouts in a Chevron Orifice and Them Impact on the Acoustic and Flow Parameters of Synthetic Jet
Round 1
Reviewer 1 Report
Some remarks are hand written in the attached pdf file.
Courious why circular holes were used, when it is known that they do not work well from the point of view of noise. The use of chevrons seems less important than the shape of the orifice.
Relatiely long orifice, from my point of view.
Could an orifice (oval, circular) with chevrons not on the top but in the inner channel do some job?
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
thanks for the positive feedback on my paper. Below is a list of my answers.
Reviewer: Courious why circular holes were used, when it is known that they do not work well from the point of view of noise. The use of chevrons seems less important than the shape of the orifice.
Answer: Actually the use of a square orifice gives the higher noise reduction, about 5.7dB (see https://doi.org/10.3390/app11104600). However, the shape of the orifice impact also on the other parameters of SJ. For example, the square orifices are the best in heat exchanged. Therefore, I decide the investigates a circular orifice. Additionally, his paper was a natural consequence of the paper: Smyk, E.; Markowicz, M. Acoustic and flow aspects of synthetic jet actuators with chevron orifices. Appl. Sci. 2021, 11, 652, doi:10.3390/app11020652.
Reviewer: Relatiely long orifice, from my point of view.
Answer: As I suppose, it is about the division of the orifices into long and short. Of course, the concept of the long and short orifice is contractual. For me, the long orifice is an orifice with the length to diameter ratio t/d>1.
Reviewer: Could an orifice (oval, circular) with chevrons not on the top but in the inner channel do some job?
Answer: I'm not sure what do you mean by "inner channel". I think about the additional nozzle/orifice in the actuator cavity (I can't find the article I am thinking of). I think that the noise reduction will be small, if at all.
I find it interesting to use a star-shaped orifice. However, the use of the new type of orifice needs investigation of SJ formation but I do not have access to PIV at the moment. In my opinion, PIV is the best for that.
Reviewer 2 Report
Please see attached PDF file.
Comments for author File: Comments.pdf
Author Response
Please, see attachment.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The author studied the impact of chevron nozzle or orifice on noise reduction and flow parameters of synthetic jets. Actuator efficiency was measured using the time-mean reaction force method.
Sound pressure level and flow parameters measurement techniques were not explained properly. Nowadays, flow parameters were measured using advanced techniques like Pressure measurements, Hotwire techniques, Holography, PIV, PTV, etc. However, the author never used even flow visualization (noninvasive techniques) in this paper. I could not see any velocity distribution and pressure distribution plots of the SJ at the nozzle exit. How can the author claim this modification create an advantageous or disadvantageous impact on the synthetic jets? The noise reduction in SJ without studying the flow properties at the exit of the nozzle is not good enough in my point of view. I request the author to perform some measurements (qualitative or quantitative) on the impact of the chevron nozzle or orifice on flow structures of the SJ. Most of the papers cited in the introduction explained noise reduction in aircraft. Of course, I agree with the author's statement that a chevron nozzle is a significant option for noise-reducing applications. However, the impact of the chevron nozzle on SJ is not explained clearly. So that, the introduction of the paper is not good enough. The experimental data submitted in the article is insignificant without validating the results with flow parameters. In simple words, study the flow behavior of the SJ for all cases and report the significance. Also, this paper wasn’t written carefully by the author. I could see a lot of minor careless mistakes in many places in this paper. For instance, in line 12 (even in the abstract), I can see “time-mean reaction force metho was used to measured”. I would like to say that this could be a very good article if you consider my suggestions.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The author correctly addressed all my comments and questions but the manuscript still needs a minor revision of the english language.
Author Response
Thanks for the positive feedback on my paper. The article was re-checked and the detected errors were corrected.
Reviewer 3 Report
Author made changes in the revised manuscript. but still this articles needs to be corrected. I recommend to publish this article with minor changes.
Comments for author File: Comments.docx
Author Response
Please see attachment.
Author Response File: Author Response.docx
