Research on the Flow and Transmission Performance of Magnetorheological Fluid between Two Discs
Round 1
Reviewer 1 Report
As per the title of work, detailed flow study must be presented. However only plot has been presented to represent the flow.
Main question addressed by the research is "MR fluid flow between two disk". Yes,it is interesting.
The topic is original. It add flow of MR fluid between two disks.
The paper is well written. It is easy and clear to read.
Conclusions are not consistent with the evidence and arguments presented. Main questions are not fully addressed.
Author Response
Please see the attachment 1.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
These authors consider the role of magnetorheological (MR) fluids in
mechanical devices such as dampers, brakes, etc.
As fluids that can exhibit a high yield stress in the presence of a
magnetic field (but low yield stress in the absence of such a field),
it stands to reason that magnetic fields can be used to manipulate how
readily MR fluids transmit shear stress and hence manipulate
mechanical device response.
The authors combine theory, simulation and experiment in an effort to
understand these fluids.
This work could be published after correction.
page 3: the authors should comment on the validity of the steady state
assumption; what about start up/shut down situations? Also fluid
inertia seems to be neglected here, but I couldn't see that assumption
stated explicitly
page 3: equations are introduced with no references to literature,
symbols like eta are left undefined (probably an effective viscosity),
and I am not sure that the authors have the equations entirely correct
in any case; if v_theta really is r omega(z) about the entire
circumference it is difficult to see how p can vary with theta; in a
case like that variation of p with theta would be precluded on
symmetry grounds
page 4: authors refer to the yield surface being at sigma_r,theta =
tau_y(H), where tau_y is a yield stress but H is undefined (probably a
magnetic intensity). In any case isn't the dominant stress here the
z,theta stress rather than the r,theta stress?
page 4: The notation using a different symbol for shear stress (tau)
and normal stress/pressure (sigma) could cause confusion
page 5: despite the authors' claim that equation (13) follows from
equation (2) and (11), this does not seem to be the case and the
relation between those various equations is unclear
section 3.1 in general: for the kinematics that the authors describe,
I would have thought omega_1 = omega_2 for a system that is not
yielding and omega_1 not equal to omega_2 for a system that is
yielding; effectively that is what the authors deduce in section 3.2,
meaning that much of section 3.1 is unnecessary. Indeed many of the
results in section 3.2 could have been derived without reference to
much of the discussion of section 3.1
page 5: the claim that ``the Bingham model can only effectively
describe the rheological properties of the post-shear yield region''
is incorrect; before materials shear, there is not a distinction
between Bingham model and Herschel-Bulkley
page 5: a shear stress might be generated by MRF viscosity, but the
authors are incorrect to claim that a shear yield stress is
generated by MRF viscosity
page 6: is equation (24) an equation for for tau(H) or for tau_y(H)?
page 6: introduces a ``simplified model of the magnetic circuit'',
without us having been told why having such a model is relevant;
presumably the aim is to compute magnetic intensity H, but references
are not cited for key equations e.g. equation (27), and symbols like N
and I are not defined until several equations after they are first
introduced
page 8: ``From Equation. (16), it is known that the required minimum
shear yield stress tau_min is 37.67 kPa'': it is difficult to see how
this follows from equation (16); in any case the shear yield stress
surely depends on the magnetic intensity, and figure 3 suggests much
smaller yield stress values than 37.67 kPa can be obtained (at low
magnetic intensities)
page 8: equation (5) is meaningless because the yield thickness h_tau
is never defined
page 8: NI is quoted as 1500: what units?
page 9: ``To improve the calculation accuracy, the Finite Element
Method (FEM) is used to analyze the magnetic field in the whole
working gap'': we are never told which equations are being solved via
the finite element method, nor what the numerical parameters
(e.g. number of elements) used in the finite element method are; these
finite element results cannot be reproduced without that information
page 9: the relationship between the geometry of figure 6 and the
geometry of the device being modelled (as shown in figure 1) is not
made clear
page 9: the work ``current'' appearing on figure 7 is difficult to
read
page 10: how can dp/dtheta have units of MPa/m (before equation (31))?
Shouldn't dp/dtheta have the same units as pressure itself? Units of
dp/dtheta need to be reported in figure 8(a) legend
page 10: figure 8(b) is meaningless without being told the flow
conditions (e.g. which dp/dtheta) to which it corresponds; also in
figure 8(a) and 8(b) presumably you are presumably plotting against
distance across the gap (not against thickness of the gap)
page 10: how is equation (31) derived? is it based on a Newtonian
assumption with Newtonian viscosity eta? If so, what eta value did you
assume?
page 10: reference is made to regions 1--3 and regions and 5,
but where are these regions shown on a diagram of the device
page 11: the experimental study presumably could not be reproduced
without knowing which specific magnetorheological fluid was employed;
the authors do not tell us
page 12: ``the zero-field viscosity and rheological properties of the
MRF decreased.'' -- this sentence is unclear; decreased over time?
what does it mean in any case for a rheological property to ``decrease''?
page 12: ``reluctance'' -- it is a bit late in the manuscript to be
introducing the term reluctance (or ``magnetic reluctance''). Authors
would be better to introduce the concept (with suitable references)
back in sections 4.2--4.3 where they discuss concepts from magnetism
page 12: conclusions refer to a quadratic polynomial relationship, but
no quadratic relationship is presented in the manuscript
Author Response
Please see the attachment 2.
Author Response File: 
Author Response.docx
Reviewer 3 Report
- The working gap thickness and the yield thickness should be defined well.
- The objective function should be clearly provided in the optimization of the magnetic field structure.
- The reason why the error between the analysis and measurement shown in Figure 11 is much higher in low current than that in high current should be clearly discussed.
- This reviewer suggests the authors to perform torque control of the proposed disc system. For example, use a simple PID controller to track a sinusoidal torque trajectory. This can improve the quality of this paper.
Author Response
Please see the attachment 3.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The manuscript has been modified well. It can be accepted.
Author Response
Dear reviewers,
Thank you for giving us the opportunity to submit a revised draft of the manuscript “Research on the Flow and Transmission Performance of Magnetorheological Fluid between Two Discs (applsci-1576382）” for publication in the Applied Sciences. We appreciate the time and effort that you dedicated to providing feedback on our manuscript and are grateful for the insightful comments on and valuable improvements to our paper.
We have incorporated most of the suggestions made by the reviewers. Those changes are highlighted within the manuscript. Please see below, for a point-by-point response to the reviewers’ comments and concerns. All page numbers and chapter number refer to the revised manuscript file with tracked changes. Here below is our description on revision according to the reviewers’comments.
The reviewer’s comment 1: As per the title of work, detailed flow study must be presented. However only plot has been presented to represent the flow.
The authors’ Answer 1: In response to the reviewer's comments, we have rewritten section 4.4 of the paper to address the flow of magnetorheological fluids in different states and rewritten the conclusions. The main purpose of this paper is to study the effect of shear thinning of magnetorheological fluid in the working gap on the output torque and speed of the transmission, and to verify the theories in the paper through experiments, so the study of the flow rate is not deeply involved. According to the reviewer's comments, we will make improvements in the subsequent study.
The reviewer’s comment 2: Conclusions are not consistent with the evidence and arguments presented. Main questions are not fully addressed.
The authors’ Answer 2: The summary has been reworked for the revised article.
