An Experimental Study of the Aeroacoustic Properties of a Propeller in Energy Harvesting Configuration
, Edoardo Martellini 1, Robert Nederlof 2, Tomas Sinnige 2 and Tiziano Pagliaroli 1,*
Round 1
Reviewer 1 Report
The manuscript was about the aeroacoustic properties of a standalone three-blades propeller in and energy harvesting condition. The topic could be useful in many areas but there are some points that the authors will need to provide further details or clarify before the manuscript can be recommended to be published in the journal Fluids. Specific comments are given below.
1) The literature survey in general is not relevant to the topic of the manuscript. In my point of view, I think the literature review should be more focusing on aerodynamics of propeller and the research on noise generation and suppression on different propellers rather than discussing powertrains in hybrid aircraft.
2) Experimental setup is a bit weak. A schematic diagram should be included to illustrate the complete experiment setup. I.e. It is impossible to undestand the exact setup adopted in the study without knowing any dimensions. In addition, as the authors suggest that the noise reflected from the ground of the wind tunnel will affect the results obtained. In this sense, it is unclear why the authors did not attempt to filter out the reflected noise or if it is impossible to do so, why the authors did not provide any statement about how would the reflected noise affect the results and by how much? Without knowing this information, it is not really feasible to judge the correctness of the results present in the manuscript as it is a major source of experimental error.
3) Similar to point 2 above, the authors did not quantify uncertainty of individual components in the wind tunnel tests and hence, the overall experimental uncertainty. In this sense it is impossible to judge the accuracy of the data obtained from the wind tunnel tests.
4) Experimental procedures were not clearly described. For example, how long did the authors run the wind tunnel per test and did the authors repeat the experiments to test for repeatability? Also, the propeller seems quite large compared to the cross-section of the wind tunnel. What is the overall blockage ratio and did the authors use any corrections to make adjustments on the data which obtained should the blockage was too much?
In my point of view, it is critical to provide more details on the experimental setup and to conduct a more proper analysis to the measurement uncertainties before the manuscript can be recommended to be published in the journal Fluids.
Author Response
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Reviewer 2 Report
In this study, the authors investigated the noise propagation from propeller blades via experimental analysis to capture the details of sound emission in energy harvesting format.
- What kind of airfoil is used in this study? As shown in Figure two, it looks like a NACA airfoil. Do these NACA airfoils have application in propellers too? It must be clarified.
- Figure 3 (a-c) is very clear and obviously we have a peak in PSD at f=1. It is recommended to remove these figures.
- There are similar studies using airfoils to investigate PSD on their surface. Such as: https://0-doi-org.brum.beds.ac.uk/10.1016/j.renene.2022.04.052 , and https://0-doi-org.brum.beds.ac.uk/10.1016/j.energy.2021.122988 . So, the literature review can be improved by referring to these recent studies done on various airfoils using harmonic oscillations.
- Figure 7 pictures are too small. In addition, what is the energy% reported in this figure for different mode numbers? Physical discussions are essential.
- Probability density function for different pressure signals is provided in figure 8. What is the difference between regenerative and Gaussian profiles? Why are the same? Measurement techniques with their uncertainties must be reported.
- Calibration methods of the experimental measurement tools should be provided.
Author Response
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Round 2
Reviewer 1 Report
The authors did not provide very detailed answers to address my comments.
Author Response
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Reviewer 2 Report
My comments are not fully covered by the authors. Thank you.
Author Response
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