Experimental and CFD Characterization of a Double-Orifice Synthetic Jet Actuator for Flow Control
Round 1
Reviewer 1 Report
The paper “Experimental and CFD characterization of a double-orifice synthetic jet actuator for flow control”, provides on the one hand an experimental and numerical characterization of double-orifice synthetic jet actuators and on the other it can contribute to designing the flow control and jet cooling applications that uses this type of actuators. The paper presents a high degree of novelty. These applications will be of great importance in the future. In my opinion, the paper is interesting for industry, and for science.
Among the remarkable results, we can name:
- The study of the effect of the distance between the orifices;
- Direct numerical simulations (DNS) of the flow field generated by the device at the actuation frequency, which may lead to maximizing the jet output.
Following the review of the paper "Experimental and CFD characterization of a double-orifice synthetic jet actuator for flow control", we can conclude that:
- The paper contains all type of the equipment’s that are used in order to obtain the experimental values, except for the type of piezo-element, but is not highlight all the measurement conditions for achieving the experiments. However, it is necessary to present in the paper very accurately the whole scheme of measurements and experimentation, in order to obtain all the experimental values. Also, the paper must present the complete electrical connections. In this sense, no relevant figure is presented. Additional figures in this respect would be desirable;
- Please explain a little bit more detailed how the excitation signal is applied to the piezo-element by piezoelectric electrodes;
- More aspects of the experimental methods are necessary, to add in the paper. It would be interested to authors highlight all limitations of their experimental methods developed in this paper. A comprehensive discutions about experimental methods and this limitations is necessary, to add in the paper. Also, it is necessary for the authors to improve the discussion regarding the calibration of the measurement system and the reproducibility of the obtained values (and relative to the manufacturing dispersion of piezoceramic elements);
- As the authors themselves says, „The actuator was completely assembled in house: it consists of a piezo-element (realized by PIEZO Inc.), which is glued on the bottom surface of a brass membrane using a two-component silver-filled epoxy resin (EPO-TEK E4110-LV)”, but no relevant figure of the entire actuator that is the object of study of this paper is presented. It is necessary to remedy these deficiencies of the paper by presenting a relevant figure of the entire actuator that is the object of study of the paper;
- The paper is specified as piezo-element (realized by PIEZO Inc.) the type of piezo-element that is used. However, the paper does not contain all the physical characteristics of piezo-element and the piezoelectric material that used. The paper remains at this level. It is necessary to remedy these deficiencies of the paper by specifying all the physical characteristics for piezo-element and the piezoelectric material as well as its characterization. In the Table 1 it is specified only a small part of these aspects.
- In the paper, the characterization of the “working fluid” is not reported. It is necessary to remedy these deficiencies of the paper.
- A correctly and also complete formulated nomenclature, which contains all the physical quantities involved in the paper along with the measurement units in the international system, is necessary to be introduced in the paper. Thus, the readers can more easily clarify physical quantities involved in the paper;
- It is elegant as a subchapter be finished with a comment and not a figure. In this regard, a comment must be added after Figure 11 and Figure 13;
- It is necessary to present in the paper what were the criteria for choosing the frequency f, in the range of 1 Hz to 2500 Hz in the case of experiments and numerical simulations performed. There are no references to bibliography in this regard;
- The conclusions of the paper (please refresh the title: “Conclusions”) must be comprehensive and well-organized information; the paper contains many valuable results that need to be highlighted in the conclusions. The conclusions of the paper must contain the possible implications of these study in future practical developments. What are the prospects for capitalizing on this research? It is necessary to add and these aspects to the conclusions.
Author Response
Please see attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present paper “Experimental and CFD characterization of a double-orifice synthetic jet actuator for flow control” deals with experimental and numerical modelling for characterization of double-orifice 2 synthetic jet actuators for flow control.
The research is interesting and adequate for the journal, but some observations are proposed by this reviewer:
- In this reviewer opinion, abstract should state the novelty and interest for readers of the work.
- This section is well presented, with pertinent references. In this reviewer opinion authors should indicate the main objectives of their work in this section
- Experimental and numerical methodology. This section is well presented, but in this reviewer opinion, it should be part of materials and methods section.
- Experimental evaluation of the actuator frequency response. This section is well presented, but in this reviewer opinion, it should be part of materials and methods section. Furthermore, some more clear explanation about experimental actions would be welcome.
- Effect of orifice spacing via Direct Numerical Simulation. In this reviewer opinion, this is a section related to Analysis of results. It is an interesting section and the proposed comparisons are very enriching for the researches. Nevertheless, in this reviewer opinion a deeper analysis of comparison between experimental and numerical results would be welcome.
- Conclusion and future work. This section is also well presented. In this section authors could resume the degree of achievement of their objectives and the novelty of their work.
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper titled "Experimental and CFD characterization of a double-orifice
synthetic jet actuator for flow control" includes an experimental and numerical analysis of flow sintetic jet actuator.
Experimental part was performed using Dantec Dynamics MiniCTA system, which is, in fact, preferred technique for investigation of turbulence. Since in general, the hotwire sensors have velocity, temperature and directional sensitivity, the authors should extend the experimental part with the calibration and temperature correction part.
When performing a DNS (direct numerical simulation) of flow, the Navier–Stokes equations are numerically solved without any turbulence model. This means, that turbulence evolution should be reproduced over a wide range of length and time scales. This includes several issues, among them:
- Spatial discretization.
- Time advancement.
- Boundary conditions with turbulence definition at inlet boundaries.
In general I would also ask if both (computational and experimental) method are complementary at the first place.
Author Response
Please see attached file
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The paper “Experimental and CFD characterization of a double-orifice synthetic jet actuator for flow control”, provides on the one hand an experimental and numerical characterization of double-orifice synthetic jet actuators and on the other it can contribute to designing the flow control and jet cooling applications that uses this type of actuators. The paper presents a high degree of novelty. These applications will be of great importance in the future.
Among the remarkable results, we can name:
- The study of the effect of the distance between the orifices;
- Direct numerical simulations (DNS) of the flow field generated by the device at the actuation frequency, which may lead to maximizing the jet output.
Following the review of the paper “Experimental and CFD characterization of a double-orifice synthetic jet actuator for flow control”, in the present revised form, it can be said that the paper contains all the experiments and numerical simulations needed to develop the subject announced in the title and I can conclude that:
I think that now have been solved correctly and thoroughly, for the most part the reviewers’ recommendations.
A very important recommendation to improve the paper in the present revised form, is about the Figure 1. “Exploded view of the double-orifice synthetic actuator, with indication of the main connection elements”. In my opinion, it is necessary that both in the figure and in the text of the paper to be numbered and named the main components of the actuator.
Also, have been introduced within the paper the result paragraphs. In my opinion, the paper is substantially improved.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article is ready to be accepted.
Author Response
The authors want to thank the reviewer for their suggestions, which have certainly improved the quality of the work.
With my best regards,
Andrea Palumbo
