Hydrodynamic Performance of Autonomous Underwater Gliders with Active Twin Undulatory Wings of Different Aspect Ratios

Round 1

Reviewer 1 Report

The performance of a bio-inspired autonomous underwater glider is investigated in the article. It is technically sound and contribute to the body of knowledge. The subject matter is presented in comprehensive manner and sufficient reference have been provided. There are some minor mistakes e.g. sequence of equation numbers, which needs to be fixed to improved the quality of publication. 

Author Response

Thanks to the reviewer's comment. Accordingly, we have correct the equation numbers.

Reviewer 2 Report

Review of “ Hydrodynamic performance of autonomous underwater gliders with active twin undulatory wings of different aspect ratios, “ by Yongcheng Li , Jianxin Hu  ,Qiuzhuo Zhao , Ziying Pan, and Zheng Ma

The interesting paper describes numerical simulations of a underwater autonomous glider with active twin sides wings that permit undulatory motion.

It shows results for lift, drag, and thrust forces generated by the wings and shows a linear relationship.

The paper sets apart the research from autonomous vehicle to focus on the glider to have ability for locomotive function,  a  swimming fish inspired concept.

They introduce the geometry as a factor as well (AR, aspect ratio) and seek an optimal design

General comments :

• Much of the numerical methods and meshing are taken from the authors previous published work (notably and referred to appropriately in text and references [16, 21]) .
• Appears the main design is also borrowed from those previous works, such as the bullet shape and much of the undulatory hydrodynamic wings parameters such as AR (ref. 16, and 21);
• the numerical scheme is properly used from that previous works
• Numerical scheme is claimed validated but the results should be validated (experimentally) at some point ;
• it does overall look like a replica of that previous studies by same authors with the difference in that the contribution in this paper is the wings undulatory motion and the AR effect study (although much like in [21]), which is ok, but then should just be small communication and not a full article again.
• It is a good addition and very appropriate for the JMSE Journal

Thus, the general recommendation is accepting for publication after minor changes but as ‘short communication’ and not as full article since much of it has already been published

Other suggestions/corrections:

What is time instant and how is it chosen in the vortex structure plots (Figs. 7, 8, 9) ?

What value of iso-surfaces is shown in these vortex plots (Figs. 7, 8, 9) ?

What is the logic in the choice for DT = 0.001

Seems Re = 200 implies laminar flow, needs describe it more

How does stationary grid takes care of moving boundaries ?

Where is the weight of the AUG body taken into account?

Typos, etc

f, u, P might need be ‘bold face’ for consistency? in eqns 3, 4

line 114 need fix spaces

Author Response

Please see the attachment.

Author Response File: Author Response.pdf