Evaluation of the Fluid Properties Modification Through Magnetic Fields for Their Application on Tuned Liquid Dampers: An Experimental Approach

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Reviewer's Summary：

This study experimentally investigates the impact of magnetic fields on the viscosity of low-cost magnetic fluids (e.g., sunflower oil with iron filings) and a commercial acrylic gel, aiming to enhance the performance of Tuned Liquid Dampers(TLDs). The work highlights the challenges of achieving homogeneous ferrofluids and precise viscosity control under magnetic fields, proposing magnetic fluids as a promising yet underdeveloped solution for adaptive TLDs. The manuscript presents a valuable experimental investigation into magnetic field-modulated TLDs using cost-effective materials. However, the above revisions are necessary to clarify the novelty, strengthen methodological transparency, and deepen the interpretation of results. With these improvements, the study will better contribute to the field of adaptive vibration control.

 

Suggestions for Improvement：

Comment 1:The introduction should more explicitly highlight the unique aspects of this study compared to existing research on magnetorheological fluids (MRFs) in TLDs. While the use of low-cost custom-prepared magnetic fluids is mentioned, the manuscript does not clearly show how this approach differs from prior work (e.g., cost-effectiveness, material accessibility, or scalability).

Comment 2: Regarding Tuned liquid damper or Tuned mass damper, some references need to be discussed, 10.1016/j.jfranklin.2022.07.030.

Comment 3: Include error discussion in Figure 7 (velocity vs. time plot) to visualize measurement variability.

Comment 4: Provide a schematic diagram of the experimental setup (e.g., Helmholtz coil arrangement, tube dimensions, sensor placement) to aid reproducibility.

Comment 5: The conclusion briefly mentions sedimentation and homogeneity challenges but does not propose solutions. Expand this section to discuss.

Comment 6: Potential strategies to stabilize ferrofluids (e.g., surfactants, nanoparticle coatings).

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript submitted for review is devoted to the experimental study of the influence of a magnetic field on the viscosity of magnetorheological fluids and their potential application in tunable liquid dampers. The issues raised by the authors are relevant in the context of modern approaches to passive and semi-active vibration control in building, mining and general engineering structures.

The study has a certain level of scientific novelty, since the authors propose an assessment of the viscosity of various magnetic fluids using a simplified experimental method based on the fall of non-magnetic balls in tubes filled with magnetorheological fluid. Similar approaches have already been used in previous works, and the article does not demonstrate fundamentally new theoretical conclusions or radically different experimental methods. In my opinion, the novelty lies in the choice of specific fluids and the analysis of the influence of temperature and humidity on the results of the experiments.

The experimental methodology is generally acceptable for assessing the influence of a magnetic field on the viscosity of a fluid. The use of a Helmholtz coil system to create a uniform magnetic field is justified, and analysis of video recordings of falling spheres using Tracker software allows obtaining numerical data on velocity and viscosity. However, the description of the methods does not pay enough attention to controlling the uniformity of the magnetic field, and does not consider possible variations in the results due to particle deposition in the MRF, or the inhomogeneous distribution of impurities in the liquid.

The authors use the classical Stokes equations to determine the viscosity of the liquid and the dynamics of falling spheres in a viscous medium. The equations presented are correct, but it should be noted that they do not take into account the possible influence of the anisotropy of the magnetic field or nonlinear effects that manifest themselves at high concentrations of ferromagnetic particles. Perhaps these limitations of the method should be noted in the text.

Overall, the manuscript is an original scientific work, the results of which may be useful for the development of tunable liquid dampers with magnetic control. The manuscript may be recommended for publication after minor revisions.

 

There are several questions and comments regarding the text of the manuscript.

 

1.It is important to find out and indicate in the text whether the spatial uniformity of the magnetic field was controlled and its fluctuations were evaluated during the experiment. In other words, how did the authors take into account possible variations in the magnetic field generated by the Helmholtz coils and how could this affect the accuracy of the fluid viscosity measurements? Was the Tracker software for analyzing the falling spheres in the liquid calibrated, and how was the reproducibility of the measurements ensured?

2.Why was sunflower oil chosen as a carrier for the magnetorheological fluid rather than specialized base liquids with controlled rheological properties? Specialized fluids provide controlled rheology, better dispersion of magnetic particles, and stability over time. It is important to clarify and indicate in the text whether this choice was based on experimental considerations or possibly on material availability limitations.

3.The review part of the article provides information on traditional and magnetorheological liquid dampers, their characteristics, and modeling methods. At the same time, modern numerical methods for modeling MRF in complex structural systems are not sufficiently covered. It is also advisable to add modern (for the last 5 years) studies on vibration monitoring, which should accompany the operation of dampers (for example, a method for applying the use of a smart 4 controller for the assessment of vibrations and shock loads) and add a series of studies on “class of shell dampers” and “open shell dampers” that demonstrate characteristics similar to magnetorheological dampers. It is also worthwhile to include an analysis of analytical models for predicting changes in fluid viscosity under the influence of a magnetic field and their experimental validation.

4.Sedimentation of magnetic particles in magnetorheological fluids is a serious factor that can affect the stability of their rheological properties. If this effect is not taken into account, the results of the experiment may be unstable or time-dependent. Therefore, it is important to note whether the homogeneity of the suspension was controlled and how the sedimentation dynamics under the influence of the magnetic field was studied.

5.Why do the experimental data obtained show significant variability when the magnetic field is activated, and do you see a way to reduce this variability?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Attached

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Needs modifications.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised paper still cannot be considered for publication since the corresponding response does not stick to the point of the comments. The text offers useful observations, but does not contribute to the theory of the field. Concerns continue to grow:
1. Regarding comment 1, The analysis of the proposed strategy still does not bring out the contribution effectively. 
2. Regarding comment 2, the Tuned liquid damper or Tuned mass damper theory in the recommended article should be discussed.
3. Regarding comment 4, the figure 8 is advised to be combined with figure 6 or 9.
4. The resolution of the image is low, making it very blurry, e.g., Figs. 1, 5.
5. Presentation of figures needs to be improved.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have done a great job in addressing the comments. I don't see further issues.

Author Response

The authors wish to express our sincere gratitude to the reviewer for their insightful comments, which have helped us significantly improve the manuscript.