Constructive Aerodynamic Interference in a Network of Weakly Coupled Flutter-Based Energy Harvesters

Round 1

Reviewer 1 Report

This work “Synergies and constructive interference in a network of weakly aerodynamically-coupled piezoaeroelastic energy harvesters based on nonlinear flutter”. In this manuscript, the authors present a three-dimensional study of the piezo-aeroelastic behavior of two vertically arranged harvesters. Although the topic is interesting, the following points should be improved.

 

 

• The title is very lengthy, try to shorten it (If possible).
• The abstract of the article is poorly written. The problem statement at the start of the abstract is not mentioned, abstract started with the proposed solution. It can be more concise and must be restructured. Name a few of the applications i.e., sensors that can be operated by the designed system for a better understanding of readers at the end of the abstract.

 

 

• There are many grammatical errors throughout the paper, which need to be corrected. Try to avoid unnecessary long sentences.

 

• The literature review is ambiguous; include some more recent state of the art papers in the Literature review for better understanding. Add the following paper for piezoaerolastic energy harvesting from the flutter mechanism.

 

• Elahi, H., Eugeni, M., Fune, F., Lampani, L., Mastroddi, F., Paolo Romano, G., & Gaudenzi, P. (2020). Performance Evaluation of a Piezoelectric Energy Harvester Based on Flag-Flutter. Micromachines, 11(10), 933.

 

 

• The Introduction part of the article must be revised to make it better structured for the readers. Try to explain the previous work related to different aspects of the current research and connect it with the problem statement in the end i.e. identifying the gap and why was this model necessary to develop. An intense revision is required in this section.

 

• In the last paragraph of the introduction section, mention the novelty of this paper with the previous state of the art research. Rather than mentioning the results/conclusions of the manuscript. Moreover, mention the applications of this work.
• If possible, compare the numerical/experimental data with the data already present in literature for validation in graphical form.
• Is it possible to have a bifurcation diagram from the obtained data, in order to understand the stability of the harvester?
• What type of motion for LCOs influence more towards energy harvesting? i.e., plunge motion or torsion or flap in the given case?
• Why the Quasi-steady model is considered in Fig 17. While in literature it is proven that for true prediction of energy harvesting capability of the harvester, it is important to use the unsteady model (See Ref. 11 of the manuscript).

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Submitted paper deals with the special energy harvesters based on the principle of a lifting surface made of piezoelectric material, which is vibrating in the unstable flutter regime. The study is focused on the interference of harvesters, especially on the effect of the distance between the harvesters on the flutter speed and on the other characteristics. Analytical model includes the model for unsteady aerodynamics, FEM model for the structure and the piezoelectric material, spline model for connection of both ones and finally the numerical model for the solution in the time domain.

Introductory part provides comprehensive description of the past developments in the subjected area. The description includes extensive links to the appropriate references. Next, the computational model is described. The description is structured according to the model parts, i.e. aerodynamics, structure, interconnections and numerical integrations. Model description is well structured and descriptive and is enough extensive. Numerical model verification is provided using the typical application.

Finally, the application example of the two-harvesters array is provided. The main focus is paid on the influence of the separation distance of both ones. The analytical results are presented and discussed. The conclusion part summarises the results. The main outcome is the decrease in the flutter speed for the specific range of the distance. The very last part, which is enough extensive, includes the references.

The paper describes the application of the state-of-the-art means and methods on the specific engineering application. Nevertheless, the problem is very complex and interdisciplinary. The paper is well structured and includes all required parts. The paper can be recommended for publication.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Review of the manuscript

Title: Synergies and constructive interference in a network of weakly aerodynamically-coupled piezoaeroelastic energy harvester on nonlinear flutter   

 

Overall, authors presents a computational framework to study coupled mechanical, piezoelectric and aerodynamic systems in this paper. The aerodynamic model was based on the Unsteady Vortex Lattice Method (UVLM) for the solution of the incompressible and irrational flow around the immersed bodies. In order to do, authors three-dimensional  structure was modeled as a modified Euler-Bernoulli beam (includes von Karman nonlinear strains) which can have embedded piezoelectric layers along all or parts of its length. In the next step, authors perform simulations where analysis flutter frequency and compare such obtained results with results published by De Marqui et. al. Moreover, they also considered  case of two aerodynamically coupled harvesters by assuming flutter speed equals 41.05 m/s.  The results shown in Fig. 12 indicated that vertical distance between both harvester play important role to define both zones from phenomena flutter point of view and generate maximum power from harvesters. In my opinion this manuscript apart from obtain s satisfactory simulations results should be fullfilled  about experimental tests.

 

As a result, taking into account contents of this manuscript, I encourage authors to improve it:

 

Major remarks:

1. Numerical calculations describes in Section 3 are performed for electrical resistance R=10kΩ.  Have you perform simulations for others values of resistance R? Why did you choose resistance equal 10 kΩ?

 

2. Taking into account references it is known that better performances gives the homogenized model of PEH (piezoelectric harvester). Please indicate which type of numerical model was used in simulation (mechanical model or electrical model). Moreover, I encourage authors to repeat simulations with the homogenized model of this harvester.

 

3. The obtained voltages in fig.18 achieve value close to 180V. How are you going to collect energy from the high voltage piezo-element (180V) in testing? Moreover, please indicate which piezo will be use in tests (purchased or manufactured by you)?

 

In my opinion, experimental investigations will be crucial part of this manuscript that it allows verify numerical results.  Thus, I recommend authors to perform lab tests.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The paper is in good shape now and the authors have successfully answered all questions of reviewers. It can be published now.