Dynamic Performance Analysis and Design of Vortex Array Grippers

Round 1

Reviewer 1 Report

Some important contents in the paper should be revised. First of all, please clarify the structure of the vortex gripper and exhaust vent. Especially, the explanation of the latter one is significantly missed, so the discussion in section 3.4 is hard to understand. In addition, the explanation about how the numerical analysis has been done is not clear. In the beginning paragraph of section 2, it is said that "In the numerical method, the governing equations of mass, momentum, energy, and RNG k-ε turbulence model were employed." However, only this sentence does not make sense. Please write minimally essential equations or explanations.

Author Response

Reply to reviewer’s comments

Reviewer #1

Reviewer’s Comment 1-1

First of all, please clarify the structure of the vortex gripper and exhaust vent. Especially, the explanation of the latter one is significantly missed, so the discussion in section 3.4 is hard to understand.

[Reply to comment:]

The structure of quad-vortex array grippers with exhaust vents is clarified in Figure 13.

Reviewer’s Comment 1-2

In addition, the explanation about how the numerical analysis has been done is not clear. In the beginning paragraph of section 2, it is said that "In the numerical method, the governing equations of mass, momentum, energy, and RNG k-ε turbulence model were employed." However, only this sentence does not make sense.

[Reply to comment:]

In this study, the governing equations of mass, momentum, energy, and RNG k–ε turbulence model were employed. An ideal gas and compressible flow assumption were made because of the high-pressure condition at the inlet boundary. The mass flow rate and pressure outlet boundaries were set at the inlet and outlet, respectively.

The commercial software ANSYS FLUENT is used to solve the governing equations. The present study is based on the SIMPLEC algorithm. Pressure and velocity correction schemes are implemented in the model algorithm to arrive at a converged solution when both the pressure and velocity satisfy the momentum and continuity equations. And the under-relaxation scheme is employed to avoid divergence in the iterative solutions.

The explanation of numerical analysis has been revised accordingly in section 2 and highlighted.

Thanks for the valuable comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

Provide better quality figures. Check references. Check spelling.

Author Response

Reviewer #2

Reviewer’s Comment 2-1

Provide better quality figures. Check references. Check spelling.

[Reply to comment:]

The quality of the figures has been improved and highlighted from Figure 8 to Figure 16. And the reference and spelling of the article has been checked.

Thanks for the valuable comments.

Reviewer 3 Report

This manuscript carries out a numerical analysis of the geometrical parameters of vortex array grippers. Though the subject is interesting and the paper is well written, its relevance is not enough to allow its publication because:

1) The developments presented in this manuscript are all based on numerical computations. No analytical expressions are proposed. Then the results are limited to the parametric values that have been used in the simulations and the conclusions of this paper are not general and cannot be used in other cases.

2) The merit of the manuscript is limited. It basically consists in running some numerical simulations and deducing some conclusions from this. Then experimentation would be required in order to verify the simulated results and increase the interest in the paper. 

3) Nothing is said about the software used in the simulations. Is it a commercial program? has it been developed by the authors?. 

4) It is unclear to me what the angle \theta is in Figure 1.

Author Response

Reply to reviewer’s comments

Reviewer #3

This manuscript carries out a numerical analysis of the geometrical parameters of vortex array grippers. Though the subject is interesting and the paper is well written, its relevance is not enough to allow its publication because:

Reviewer’s Comment 3-1

The developments presented in this manuscript are all base on numerical computations. No analytical expressions are proposed. Then the results are limited to the parametric values that have been used in the simulations and the conclusions of this paper are not general and cannot be used in other cases.

[Reply to comment:]

Since CFD is a developed analysis tool with high numerical reliability and demonstrates detail about the physical phenomenon, numerical computations were adopted for the investigation.

In consideration of the cost and manufacturing, the gripping task for larger and heavier objects can be achieved by gripper array. Therefore, the study of array grippers was carried out to extend the usage in different operation conditions.

Reviewer’s Comment 3-2

The merit of the manuscript is limited. It basically consists in running some numerical simulations and deducing some conclusions from this. The experimentation would be required in order to verify the simulated results and increase the interest of the paper.

[Reply to comment:]

CFD is a developed analysis tool with high numerical reliability. It is suitable for design parameter analysis to cut down the cost and the consumption of time of prototyping and experiments. This is also the main contribution of the paper. The optimization and manufacturing of the grippers are not the task of this study and will be discussed in future research. Your valuable comments will be greatly appreciated.

Reviewer’s Comment 3-3

Nothing is said about the software used in the simulations. Is it a commercial program? has it been developed by the authors?

[Reply to comment:]

In this study, the governing equations of mass, momentum, energy, and RNG k–ε turbulence model were employed. An ideal gas and compressible flow assumption were made because of the high-pressure condition at the inlet boundary. The mass flow rate and pressure outlet boundaries were set at the inlet and outlet, respectively.

The commercial software ANSYS FLUENT is used to solve the governing equations. The present study is based on the SIMPLEC algorithm. Pressure and velocity correction schemes are implemented in the model algorithm to arrive at a converged solution when both the pressure and velocity satisfy the momentum and continuity equations. And the under-relaxation scheme is employed to avoid divergence in the iterative solutions.

This is also revised in section 2.

Reviewer’s Comment 3-4

It is unclear to me what the angle \theta is in Figure 1.

[Reply to comment:]

The angle \theta in Figure 1. has been clarified.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revised manuscript and reply to the previous review comment looks fine. I hane no further question or comment this time.

Author Response

Thank you for the comments to improve the result of the article and a possible publication.

Reviewer 3 Report

The quality of the paper has not been improved. In fact, my main concerns have not been adequately addressed.

Author Response

It is known that the developments based on numerical methods may not directly extent to design cases beyond the parametric values that have been used in the simulations. This is why this research focuses on array grippers instead of single gripper for their feasible extension to large object gripping. However, an experimental study is required to verify the simulation results to its practical application and therefore they will be an object of future work.