Review Reports

Round 1

Reviewer 1 Report

In the introduction, adjoin-based shape optimization should be introduced as well.

 

In page 2, lines 67-68: What do you mean by the “polynomial method”? If you want to keep this method in the list, please cite at least one paper that uses it so the reader can dig deeper if needed.

 

Line 140: How do you make sure 90,000 grid points are enough to capture the flow field in 2D? Did you perform any grid study? Please include it if possible.

 

Line 144: Please revise the phrase: “a little sparse” grid distribution.

 

Line 146: Why do you use “pressure far-field” at the inlet? Isn’t the “total pressure” a better boundary condition at the inlet? You seem to have the inlet total pressure already measured in the experiment. Do you have some references that show this BC to be reliable? Also, what are the values you set for the inlet turbulent intensity and length scale and how did you decide those values?

 

Figure 4: The experimental and numerical results do not agree well where x/c in [0.2-0.35]. This must be due to RANS failure (and over-prediction of) the reattachment point. Please clarify that in the text as well.

 

Figure 6 is very difficult to understand. Can you revise that?

 

Figure 9: it’s basically unnecessary. It’s just 4 numbers made in 6 bars.

 

Can you comment on the reason behind the Spike in Cp at the leading edge? And why that causes a huge profile loss? (Perhaps you can consult with Goodhand’s PhD thesis)

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

In this study a new blade parametrization method is proposed for a transonic compressor cascade to control the blade profile in order to optimize he aerodynamic performance. The research is attractive for several engineering applications. The paper is quite of good in the complex, but some requests and suggestions have been provided to increase the quality of the work.

The introduction is quite complete, however is focused mainly on the history of the axial blade optimization, I suggest extending the literature background on the CFD methodologies applied also at particular conditions. For example, the flow under certain conditions, gives instability and vibrations, as the vortex shedding phenomenon. So, you could add these two works as references:

1 - Liuliu, S.; Yang, G.; Yao, S. Large eddy simulation of flow past a square cylinder with rounded leading corners: A comparison of 2D and 3D approaches. J. Mech. Sci. Technol. 2018, Vol. 32, pp. 2671–2680.

2 - Cravero, C.; Marogna, M.; Marsano, D. “A Numerical Study of Correlation between Recirculation Length and Shedding Frequency in Vortex Shedding Phenomena”. WSEAS TRANSACTIONS on FLUID MECHANICS, 2021, Vol. 16, pp. 48-62.

These shows the different turbulence models behavior on the vortex shedding phenomenon that can give a dangerous structural problem and so it must be well captured.

The reference geometry has been well described by reporting the main geometrical parameters and the control points, as well as the curves for the cascade modelling. Then I suggest adding a governing equation section (for the Navier-Stokes and turbulence models).

As regards the numerical method the mesh has been well described, however you should enlarge the figures with the grids, which have a poor quality. Moreover, you could add a figure with the y+ distribution on the blade. Do you have performed a grid sensitivity analysis? Please, you report it.

The boundary conditions are well described in a clear way, maybe you could better specify why you have chosen the SST turbulent model.

The performance parameters are reported and defined. The validation of the model has shown a good accuracy for your scope, moreover have been explained the reason for the differences found; however you could report a table with the percentage error committed.

The optimization algorithm and the optimization process are described in complete way. You should only better clarify the software used for this.

The results section is very complete with diagrams and flow contours of the different geometries. However they often are too small and difficult to read, please improve their quality.

The conclusions well resume the main results obtained in this research.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

machines-2143484-peer-review-v1

The article describes the blade shape optimization of a transonic compressor cascade to enhance aerodynamic efficiency. Different design variables on the blade surface profile and leading edge were selected as design variables and efficiency was selected as an objective function. It was shown that the pressure loss coefficient was reduced by 11% compared to the reference case. Moreover, it was found that the shock pattern is changed by changing the blade profile.

 

Comments:

The idea itself, however, is not novel, and neither is the numerical model. No novel contribution was done in the current manuscript and this paper is not original. It is not a good idea to use 2D optimization and then they have done a simple case study for a 3D model. The authors need to do optimization for the 3D model. These days by improving the computational resources, 2D CFD data is not acceptable. The current manuscript looks like an industrial report and there is no new finding, therefore I would not recommend it for journal publication.

 

 

1. It is better to add 2D optimization in the title.

2. An extensive English correction is needed, such as lines: 114-124

3. The objective of the current study is not clear. What is the novelty of the current study?

4. Fig.4: this figure clearly shows the disadvantage of the 2D model compared to experimental data. I wonder how the optimization data based on 2D simulation is trustable. This is not acceptable.

5. The authors its better to show the grid independence test.

6. More information regarding the numerical method and boundary condition is required.

 

 

 

 

 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I would like to thank the authors for responding to my comments.

Reviewer 2 Report

All my comments and suggestion have been added in the revised work. Now the paper has increased its quality and it is ready for the publication in this form.