Manufacturing of Double Layer Optical Fiber Coating Using Phan-Thien-Tanner Fluid as Coating Material

Round  1

Reviewer 1 Report

This paper concerns numerical simulations for non-Newtonian Phan-Thien-Tanner fluids in a wire-coating coextrusion problem. The subject matter is well known, the equations and boundary conditions are well known, and the results are not very interesting to our understanding of the problem. The writing is not very good, it is full of errors, and the paper should be rejected.

I found the following major errors in the first 4 or 5 pages of the paper and I gave up on reading after this.

line 72, should read “Phan-Thien-Tanner”.

line 75, should read “Mutlu”.

line 110, should read “...z is the axial coordinate”.

line 112, should read “Figure 2. Schematic of double-layer coating in the    secondary coating die”.

In the equations, drop the terms with the time-derivatives because they you do    not solve a time-dependent problem.

Eq. (5) should read rho*cp*v*deltheta=kdel2theta+tau:delv.

In eq. (6), should have dp/dz instead of dp/dt.

In eq. (8) there is no mentioning of how this equation was derived and what    are the definitions of S and lambda.

In eq. (9), there is no definition of Omega and C.

Author Response

Referee #1

Comments and Suggestions for Authors

This paper concerns numerical simulations for non-Newtonian Phan-Thien-Tanner fluids in a wire-coating coextrusion problem. The subject matter is well known, the equations and boundary conditions are well known, and the results are not very interesting to our understanding of the problem. The writing is not very good, it is full of errors, and the paper should be rejected.

I found the following major errors in the first 4 or 5 pages of the paper and I gave up on reading after this.

Q1. line 72, should read “Phan-Thien-Tanner”.

Reply: It has been done accordingly. Thank you for this notice

Q2. line 75, should read “Mutlu”.

Reply: It has been corrected. Thank you for this notice

Q3. line    110, should read “...z is the axial coordinate”.

Reply: It has been done accordingly. Thank you for this notice

Q4. line    112, should read “Figure 2. Schematic of double-layer coating in the    secondary coating die”.

Reply: It has been done accordingly. Thank you for this notice

Q5. In    the equations, drop the terms with the time-derivatives because they you do    not solve a time-dependent problem.

Reply: It has been corrected. Thank you for this notice

Q6. Eq. (5) should read rho*cp*v*deltheta=kdel2theta+tau:delv.

Reply: I compare this equations with other published papers and found to be corrected.

Thank you for this notice

Q7. In eq. (6), should have dp/dz instead of dp/dt.

Reply: It has been corrected. Thank you for this notice

Q8. In eq. (8) there is no mentioning of how this equation was derived and what    are the definitions of S and lambda.

Reply: It is the standard model used for the PTT fluid. We can validate this model by comparinf with other published papers as given in Ref. 19 and 20.

Thank you for this notice

Q9. In eq. (9), there is no definition of Omega and C.

Reply: Omega is the constant pressure gradient which is now given in Line 143 and C is the constant of integration.

Thank you for this notice

Reviewer 2 Report

The paper must be completely rewritten.

1. The quality of English is low. 

2. The text is full of typos.

3. There are elementary errors even in the formulas.

4. The analytical solution should be moved to Appendix.

5. The results should be given in graphs - tables are impossible to read. (All the tables, by the way, lack information how columns differ from each other - the column headings are identical.)

6. The quality of Figure 1 is low.  Why is not the system symmetric relative to z-axis? How can the velocity be different on the different sides of the blue line? Improve the textual and graphical description of the problem you are solving.

7. What is the novelty of the paper? What is the usefulness of the paper?

8. Explain Eq .8 much more carefully. What e.g., do you mean with “epsilon is the elongation behaviour”?

Author Response

Referee#2

Comments and Suggestions for Authors

The paper must be completely rewritten.

Q1. The quality of English is low. 

Reply: The whole paper is revised and found free of error, typos and grammatical errors.

Thank you for this notice

Q2. The text is full of typos.

Reply: It has been done accordingly. Thank you for this notice

Q3. There are elementary errors even in the formulas.

Reply: The paper is revised and all the equations and formulas has been corrected.

Thank you for this notice

Q4. The analytical solution should be moved to Appendix.

Reply: The analytic solution is now given in the appendix in the revised manuscript.

Thank you for this notice

Q5. The results should be given in graphs - tables are impossible to read. (All the tables, by the way, lack information how columns differ from each other - the column headings are identical.)

Reply: The effect of various parameters involved in the solution has been discussed is results and discussion section clearly and mentioned in the Figures now in the revised manuscript.

Thank you for this notice

Q6. The quality of Figure 1 is low.  Why is not the system symmetric relative to z-axis? How can the velocity be different on the different sides of the blue line? Improve the textual and graphical description of the problem you are solving.

Reply: Figure just shows the comparison of the analytical and numerical solutions. And from this figure it is clear that from both the method we get the same solution which also shows the validity of the proposed solution.

The Figure 1 is drawn again and the quality of the figure is improved.

Thank you for this notice

Q7. What is the novelty of the paper? What is the usefulness of the paper?

Reply: In this paper we used the non-Newtonian viscoelastic PTT fluid for double-layer optical fiber coating using a pressure type coating die. The primary coating is used to protect the fiber from microbending which is made from soft coating material and the outer coating protects the primary coating from mechanical damage. The effect of emerging parameters involved in the solution are discussed and analyzed through the tables and explained how the velocity and thickness of the coated fiber optics can be controlled through these parameters.

Thank you for this notice

Q8. Explain Eq .8 much more carefully. What e.g., do you mean with “epsilon is the elongation behaviour”?

Reply: Equation 8 is the standard model used for the PTT fluid. Yes episolon is the elongation behavior.

Thank you for this notice

Reviewer 3 Report

I would ask that the authors to consider following recommendations for a major revision:

1. Abstract: “The flow dependent on the wire or fiber velocity, geometry of the die and the viscosity of the polymer.” - Do you mean “depends”?

2. Introduction:

- Line 26 to 36 is copied from a recent publication of the same authors (Scientific Reports (2018) 8:14504) which is very unexpected and not acceptable at all.

- Similarly, line 72 to 80 contain word to word match from the same reference mentioned above.

- Check reference number in line 80. Should it be 16?

3. Paragraph starting from line 40 to 51 needs multiple references. Please include.

4. “The present flow analyzed has not been investigated previously.” - This sentence is not clear and rewording of the sentence is necessary.

5. Reference needed for mass and momentum balance equations.

6. English language of this manuscript needs improvement (spacing, spelling, sentence construction, typo, grammar). I recommend the authors to ask a native English-speaking colleague to proofread their article, or to use a language editing service.

Author Response

Referee#3

Comments and Suggestions for Authors

I would ask that the authors to consider following recommendations for a major revision:

Q1. Abstract: “The flow dependent on the wire or fiber velocity, geometry of the die and the viscosity of the polymer.” - Do you mean “depends”?

Reply: it has been corrected. Thank you for this notice

Q2. Introduction:

- Line 26 to 36 is copied from a recent publication of the same authors (Scientific Reports (2018) 8:14504) which is very unexpected and not acceptable at all.

Reply: The manuscript is revised and the line 26 to 36 has been rewritten in the revised manuscript.

Thank you for this notice

Q3. Similarly, line 72 to 80 contain word to word match from the same reference mentioned above.

Reply: It has been done accordingly. Thank you for this notice

Q4. Check reference number in line 80. Should it be 16?

Reply: Yes it is Ref. 16. It has been corrected. Thank you for this notice

Q4.Paragraph starting from line 40 to 51 needs multiple references. Please include.

Reply: The references for this paragraph are added in the caption of Figure 1. And Figure 2. As shown in the revised manuscript.

Thank you for this notice

Q5. “The present flow analyzed has not been investigated previously.” - This sentence is not clear and rewording of the sentence is necessary.

Reply: It has been accordingly. Thank you for this notice

Q6. Reference needed for mass and momentum balance equations.

Reply: It has been done accordingly. Some recent published work has been added in the revised manuscript as given below related to mass and momentum equations.

1. T. Hayat, R. S. Saif, R. Ellahi, M. Y. R. Taseer, B. Ahmad, Numerical study for Darcy-Forchheimer flow due to a curved stretching surface with Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions. Results in Physics 7:2886-2892. DOI: 10.1016/j.rinp.2017.07.068

2. T. Hayat, R. S. Saif, R. Ellahi, M. Y. R. Taseer,  A. Alsaedi. Simultaneous effects of melting heat and internal heat generation in stagnation point flow of Jeffrey fluid towards a nonlinear stretching surface with variable thickness. International Journal of Thermal Sciences 132:344-354. DOI: 10.1016/j.ijthermalsci.2018.05.047.

3. N Shehzad, A Zeeshan, R Ellahi, K Vafai. Convective heat transfer of nanofluid in a wavy channel: Buongiorno’s mathematical model. Journal of Molecular Liquids. PP: 446-455.

4. R. Ellahi and A. Riaz. Analytical solutions for MHD flow in a third-grade fluid with variable viscosity. Mathematical and Computer Modelling. PP: 1783-1793.

Thank you for this notice

Q7. English language of this manuscript needs improvement (spacing, spelling, sentence construction, typo, grammar). I recommend the authors to ask a native English-speaking colleague to proofread their article, or to use a language editing service.

Reply: The whole manuscript is revised and discuss with other experts and found it free from spacing, spelling, typo and grammatical errors.

 Thank you for this notice

Round 2

Reviewer 1 Report

The paper is much better now that the authors have taken into account the errors pointed out in the previous version. The paper although it does not add significant new understanding, it should be published as is.

Author Response

Dear Referee thanks for your comments. The paper has been checked for all typos and all the corrections are done. Thanks for your acceptance.

Reviewer 2 Report

There are still too many typos and errors, also in Formulas (both in the text and Appendix), to list them all. It is the author’s duty read the text very carefully and correct them. E.g. -        Formulas 1-4 and 6. - Line 362 and 363 not H1 but H_1 (subscript) -Line 122 Check if the factor 1/2 needed. -Line 122 Eq.(6) not Eq.(5) -In some places cured not curved. -        Line 132 “after simplification become where”. Become what? font sizes vary -Dimensionless parameters Br and De should be in normal text font, ln too. etc.  The quality of Figures 1, 2, 3 is low.  Figure 1 should be Figure 2 and vice versa.  Figure 1 is incorrect. The flow fields of the two coatings are continuous. See  Figure 4.  Figure 3 Use logarithmic scale. Comparison of what? In what conditions?  Formula 5. Write down what is theta.  Formula 8: Explain this equation. What is S? What is stress function f? What is epsilon (scalar/function)? What is lamda (scalar/function)? Explain accurately. E.g. “epsilon is the elongation behavior” does not mean anything.  Line 129 How can epsilon = 0 and lamda = 0  in Eq.(8) lead to different models? Are they in S?  Line 132 What is omega?  Line 138 Explain the physical meaning of the dimensionless parameters. Formula 19. What is gamma? Line 138 and line 168. Do you have two different Deborah numbers? Line 173 “This figure shows that as the pressure gradient parameter increases the velocity profile increases.” This is totally trivial. Isn’t there anything else to say? Is there e.g., any nonlinearity? Line 175 “It is noted that the velocity follows as increasing trend with increasing Deborah number.” What is the physical meaning? Why? (This sentence is also another example of typos.) Line 176 “The nonlinearity in velocity profiles appear for the large values of”. How do you see that? What is the consequence? Line 177 “The velocity inside the die exceeds from the fiber optics velocity due to large values of the Deborah number.” This happens in three cases in Figures 4 and in all cases in Figure 5, and not only due to large De. Line 178 “This is may be due to combine effects of force due to moving optical fiber and non-zero imposed pressure gradient.” How could the moving optical fiber have effect on it? Line 180 “Such phenomena may not be possible in the absence of imposed pressure gradient.” This is trivially not possible without an imposed pressure gradient. Not only “may not”. Line 138 Is definition of dimensionless r^star correct? Shouldn’t it read r^star = r/R_w?  In figures 3, 4 etc. you should have dimensionless r^star, not r, on x-axis. Right?  Isn’t origin at the middle of fiber (see Figure 1)? Why is the r-scale in figures 3, 4 etc. from 0 to 1 and in Figure 3 from 1 to 2? Should not it always be from 1 to 2?  Figure 6. Delta is constant and delta is on the x-axis??  There are many figures. You should clearly explain the reason of each figure. What does one learn (excluding trivialities)? Clear connection to the real process is needed.  Change Tables 1 and 2 to figures. Remove Table 3. Explain verbally. In conclusions, what did we learn? What is the novelty of the paper? What is the usefulness of the paper? Is the model good enough for simulating practical processes? How could it be improved? How should/shouldn’t one run the coating process?

Author Response

Please see the attached file.

Thanks

Author Response File: Author Response.pdf

Reviewer 3 Report

An acceptance of the manuscript is recommended. 

Author Response

Dear Referee thanks for your comments. Thanks for your acceptance.

Round  3

Reviewer 2 Report

There are still too many words lacking, typos and errors, (both in the text and Appendix), to list them all. It is the author’s duty READ the text VERY CAREFULLY and correct them. Just two examples

Line 362 and 363 not H1/H2/H3 but H_1/ H_2 / H_3 (subscript)

STILL in one place cured not curved.

In many cases the authors have answered to the referee, but haven’t added their comments in the text. I repeat such questions again.

Figure 3 Comparison of what? In what conditions? Explain in the text.

Line 174 Explain the physical meaning (Brinkman, Deborah etc.) of the dimensionless parameters in the text.

Formulas 31 and 32. What is gamma? Explain in the text.

Line 208 “The nonlinearity in velocity profiles appear for the large values”. How do you see this? What do you mean with this? Explain in the text.

Line 207 “It is noted that the velocity follows as increasing trend with increasing Deborah number.” What is the physical meaning? Why? Explain in the text.

Line 209 “The velocity inside the die exceeds from the fiber optics velocity due to large values of the Deborah number.” This happens in three cases in Figures 4 and in all cases in Figure 5, and not only due to large Deborah number. Explain in the text.

Line 178 “This is may be due to combine effects of force due to moving optical fiber and non-zero imposed pressure gradient.” How could the moving optical fiber have effect on it? Explain in the text.

Line 180 “Such phenomena may not be possible in the absence of imposed pressure gradient.” This is trivially not possible without an imposed pressure gradient. Not only “may not”. Explain in the text.

In all figures one should have r_star, not r. The authors responded: “Here we used in Figure 3,4,ect r because after simplification the asterisk has been removed.” I do not understand. Isn’t the solution made in non-dimensional form?

In Figure 6, 10, and 11 Delta is constant and delta is on the x-axis??

The practical aspect of the paper is still lacking: There are many figures. You should clearly explain the reason of each figure. What does one learn (excluding trivialities)? Clear connection to the real process is needed.

In conclusions, what did we learn? What is the novelty of the paper? What is the usefulness of the paper? Is the model good enough for simulating practical processes? How could it be improved? How should/shouldn’t one run the coating process?

Author Response

Please see the attached file.

Thanks

Author Response File: Author Response.docx

Round 4

Reviewer 2 Report

Q1. Figure 3 Comparison of what? In what conditions? Explain in the manuscript what where the numerical conditions of this comparison.  Q2. Line 226 “From figures 4 and 5 it is  clear that nonlinear behavior is occurred in the velocity profiles. Since the velocity of fluid first increase up to a certain values and then decreases which shows the shear thickenings effect”.  I don’t understand this. What do you mean with this? Explain again in the manuscript. Q3. Line 232. “Such phenomena may not be possible in the absence of imposed pressure gradient because if the imposed pressure gradient is zero.” This is trivially not possible without an imposed pressure gradient. Not only “may not”.  Remove this. Q4. Is the fiber moving in the simulation? If it is, how can the velocity be zero at fiber wall  r^star=1 (Figures 4 and 5). Q5. I don’t understand  figure 6. How can volume flow rate depend on position r^star? Q6. How is the thickness of the coated fiber optics or coating thickness (h_c) defined and calculated? (Figures 10 and 11). Q6. The practical aspect of the paper is still lacking: There are many figures. You should clearly explain the reason of each Figure in the manuscript. What does one learn (excluding trivialities)? Clear connection to the real process is needed. Q7. In Conclusions section, explain what did we learn. What is the novelty of the paper? What is the usefulness of the paper? Is the model good enough for simulating practical processes? How could it be improved? How should/shouldn’t one run the coating process? Explain in the manuscript.

Author Response

Review Report

REPLIES TO THE REVIEWER’S COMMENTS

The authors are grateful to the reviewers for their positive comments and suggestions.

Referee Comments

Comments and Suggestions for Authors

Q1. Figure 3 Comparison of what? In what conditions? Explain in the manuscript what where the numerical conditions of this comparison. 

Reply: Here we used two methods Analytical and Numerical. Figure 3 shows that from both method we get the same solution which confirm that the our results are true. The numerical values to the emerging parameters are now given in the latest version.

Thank you for this notice

 Q2. Line 226 “From figures 4 and 5 it is  clear that nonlinear behavior is occurred in the velocity profiles. Since the velocity of fluid first increase up to a certain values and then decreases which shows the shear thickenings effect”.  I don’t understand this. What do you mean with this? Explain again in the manuscript.

Reply: From figures 4 and 5 it is clear that nonlinear behavior is occurred in the velocity profiles. Since the velocity of fluid first increase up to a certain values and then decreases which shows the shear thickenings effect. For low elasticity means for low Deborah number the velocity disparity diverges little from the Newtonian one, however when Deborah number is increased, then profiles turn into more flattened showing the shear-thinning effect. It can be seen that as is reduced, these profiles turn to the Newtonian one and the result is therefore independent of . This also explain in the revised manuscript.

Thank you for this notice

Q3. Line 232. “Such phenomena may not be possible in the absence of imposed pressure gradient because if the imposed pressure gradient is zero.” This is trivially not possible without an imposed pressure gradient. Not only “may not”.  Remove this.

Reply: this sentence has been removed. Thank you for this notice

Q4. Is the fiber moving in the simulation? If it is, how can the velocity be zero at fiber wall  r^star=1 (Figures 4 and 5).

Reply: yes the fiber moving with constant velocity. At the fiber wall the velocity is not zero it is start from 1. Since the interval is 0-20 in Figure 4, so it seems that it starts from zero basically it starts from one. Similarly in Figure 5.

Thank you for this notice

 Q5. I don’t understand  figure 6. How can volume flow rate depend on position r^star?

Reply: The formula to calculate the volume flow rate is [17]

It depends on the position It has been corrected in the latest version.

Thank you for this notice

Q6. How is the thickness of the coated fiber optics or coating thickness (h_c) defined and calculated? (Figures 10 and 11).

Reply: the thickness of the coated fiber optics has been calculated by the following formula [17]

Thank you for this notice

Q7. The practical aspect of the paper is still lacking: There are many figures. You should clearly explain the reason of each Figure in the manuscript. What does one learn (excluding trivialities)? Clear connection to the real process is needed.

Reply: The full explanation is given in the results and discussion section. Each parameter has been explained physically and the effect on velocity, temperature and thickness of the coated fiber optics.

Thank you for this notice

 Q8. In Conclusions section, explain what did we learn. What is the novelty of the paper? What is the usefulness of the paper? Is the model good enough for simulating practical processes? How could it be improved? How should/shouldn’t one run the coating process? Explain in the manuscript.

Reply: This is a new paper in which we explain that the PTT fluid can be used for the double-layer optical fiber coating for the manufacturing purposes. No one has used PTT fluid for the fiber coating using wet-on-wet coating process. It is our first attempt to model PTT fluid as a coating material for double-layer optical fiber coating using wet-on-wet coating process. The complete procedure is also given in Figure 1. The coating provides protection from mechanical damage and from signal attenuation. Since there is no laboratory facilities this is total on theoretical basis. That why for the validation the present work is also compared with published work by taking the non-Newtonian parameter tends to zero and strong agreement is found. This model is also enough for simulating practical processes. Since the PTT fluid is highly viscous fluid so it is sufficient good to use for coating purposes. The coating process is completely given in the revised manuscript as mentioned in Figure 1.

Thank you for this notice

Once again the authors are grateful to reviewers and editor for their constructive comments and suggestion and for spending time on reading and improving the manuscript.

We look forward for a positive response regarding our revision.

Yours sincerely

Dr.Haroon Ur Rasheed

Author Response File: Author Response.docx