Effect of Turbulence Inhibitors on Molten Steel Flow in 66-Ton T-Type Tundish with Large Impact Area
Round 1
Reviewer 1 Report
The main goal of the authors of the article was to determine the effect of turbulence inhibitors on molten steel flow in 66 tons of tundisch. In the introduction the authors describe very precisely the current knowledge in this area in the world. Numerical simulations are also described in great detail. The main result that follows from the article is the finding that turbulence inhibitors with internal ripples are more advangeous (1).
The article is written very good but for a person who deals with continuous casting but does not have deeper knowledge of the theory of simulation, after a few pages read, the article can be tiring.
I would leave it to the authors´discretion to shorten the article.
My questions:
1) What tracer was used in numerical simulation? It follows from table 1 (density and viscosity) that the steel was tracer, isn´t it? Does it make sence for the same steel to be used as the tracer? In what amount?
2) What tracer was used in hydraulic experiment? KCl? In what amount?
3) Will be turbulence inhibitor (1) used in the construction of the 66 ton tundisch in China?
Author Response
Response to Reviewer 1 Comments
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Effect of turbulence inhibitors on molten steel flow in 66 ton T-type tundish with large impact area” (ID: metals-883805). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to your comments are as flowing:
Point 1: What tracer was used in numerical simulation? It follows from table 1 (density and viscosity) that the steel was tracer, isn´t it? Does it make sence for the same steel to be used as the tracer? In what amount?
Response 1: In the numerical model, tracer, as a human-defined virtual phase, was consistent with physical properties of steel.
The inlet boundary condition of the tracer mass fraction was stated as follows: when t ＜ 1s, the tracer mass fraction was set to 1, and when t > 1s, the tracer mass fraction was set to 0.(Lines165-167)
Point 2: What tracer was used in hydraulic experiment? KCl? In what amount?
Response 2: 250ml KCL was used in hydraulic experiment.
Line 197-198: “250ml KCl” was added.
Point 3: Will be turbulence inhibitor (1) used in the construction of the 66 ton tundisch in China?
Response 3: Turbulence inhibitor (1) has already used in the construction of the 66 ton tundish in China.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.
We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
All in all, the presented study is relatively interesting, but there are some major shortcomings:
1) The Abstract and Introduction are extremely hard to read
2) The English is really bad, the paper has to be proof-read
3) No mesh-independence study was presented and no details on the mesh elements were given. Which cell type was used in the presented study?
4) It has to be clarified if it is valid to simulate only half the geometry using a "Symmetry" boundary condition. The best way to do this would be to simulate the whole geometry and evaluate the results in comparison to simulations of the half geometry
5) The quality of figure 5 has to be improved, some of the text is not readable
6) Why was the standard k-epsilon-model selected for turbulence modeling? Wouldn't the realizable k-epsilon-model be more favorable?
7) The walls play an extremely important role in this study, especially for the turbulence inhibitors. How were the walls and boundary layers modelled in numerical calculations?
8) Why was a "velocity inlet" selected for the inlet boundary condition? This introduces an even velocity profile at the inlet while, in reality, this profile would be uneven (developed velocity profile). This should be improved.
9) Further, the inlet boundary condition is very close to the region of interest. In this case, special care has to be taken in order to avoid negative influences on the results provided by the boundary condition. This was not done by the authors.
10) Slag viscosity is strongly dependent on temperature. Is it valid to perform calculations of an isothermal model?
I also have major concerns on the novelty and the impact of the work:
a) Simular experiments have already been performed more than a decade ago, for example consider the paper "Water Modeling of Optimizing Tundish Flow Field" by Liu et al. (2007)
b) The simulations and experiments provided in the paper "Optimization of flow, heat transfer and inclusion removal behaviors in an odd multistrand bloom casting tundish" of Fang et al. (2020) appear to be very similar to the presented work.
Therefore, I can only recommend to reject the paper.
Author Response
Response to Reviewer 2 Comments
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Effect of turbulence inhibitors on molten steel flow in 66 ton T-type tundish with large impact area” (ID: metals-883805). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to your comments are as flowing:
Point 1: The Abstract and Introduction are extremely hard to read.
Response 1: We have made correction according to the Reviewer’s comments.
Point 2: The English is really bad; the paper has to be proof-read.
Response 2: We have made correction according to the Reviewer’s comments.
Point 3: No mesh-independence study was presented and no details on the mesh elements were given. Which cell type was used in the presented study?
Response 3: Mesh-independence study draws lessons from the paper "Numerical simulation of transient multiphase flow in a five-strand bloom tundish during ladle change" of Zhang et al. (2018). The study was the most basic and without novelty.
Lines 156-157: A more detailed description of the mesh was added.
Point 4: It has to be clarified if it is valid to simulate only half the geometry using a "Symmetry" boundary condition. The best way to do this would be to simulate the whole geometry and evaluate the results in comparison to simulations of the half geometry.
Response 4: In recent years, the "Symmetry" boundary condition was often used in the simulation of multi-strand tundish due to the symmetry of tundish structure. For example, (1) "Optimization of flow, heat transfer and inclusion removal behaviors in an odd multistrand bloom casting tundish" of Fang et al. (2020); (2)"Numerical simulation of transient multiphase flow in a five-strand bloom tundish during ladle change" of Zhang et al. (2018); (3) "A simulation study on the flow behavior of liquid steel in tundish with annular argon blowing in the upper nozzle" of Qin et al. (2018). The "Symmetry" boundary condition was still used in this paper and had not been modified.
Point 5: The quality of figure 5 has to be improved; some of the text is not readable.
Response 5: We are very sorry for our incorrect writing. The quality of figure 5 has been improved.
Point 6: Why was the standard k-epsilon-model selected for turbulence modeling? Wouldn't the realizable k-epsilon-model be more favorable?
Response 6: In recent years, the standard k-epsilon-model was often selected for turbulence model of tundish. For example, (1) "Optimization of flow, heat transfer and inclusion removal behaviors in an odd multistrand bloom casting tundish" of Fang et al. (2020); (2) "Effect of emptying time on multiphase and mixing behaviours during grade change of a five-strand bloom tundish" of Zhang et al. (2019); (3) "Mathematical analysis of the touching inclusions parameters at the tundish free Surface to predict more realistic inclusion removal rates" of Enif Gutiérrez et al. (2019). The standard k-epsilon-model was still used in this paper and had not been modified.
Point 7: The walls play an extremely important role in this study, especially for the turbulence inhibitors. How were the walls and boundary layers modelled in numerical calculations?
Response 7: It is really true as Reviewer suggested that the walls play an extremely important role in this study.
Lines 153-157: We have made correction according to the Reviewer’s comments.
Point 8: Why was a "velocity inlet" selected for the inlet boundary condition? This introduces an even velocity profile at the inlet while, in reality, this profile would be uneven (developed velocity profile). This should be improved.
Response 8: During the steady continuous casting, the ladle shroud plays an important role to deliver molten steel from the ladle to the tundish at constant flow rate, temperature, and composition. The change of velocity is not obvious in the ladle shroud. The inlet velocity, calculated by the volume flow of the inlet and the cross-section area of the ladle shroud, can effectively simulate the actual situation. In recent years, "velocity inlet" usually selected for the inlet boundary condition. For example, (1) "Numerical simulation of transient multiphase flow in a five-strand bloom tundish during ladle change" of Zhang et al. (2018); (2) "Removal mechanism of microscale non-metallic inclusions in a tundish with multi-hole-double-baffles" of Jin et al. (2018); (3) "A simulation study on the flow behavior of liquid steel in tundish with annular argon blowing in the upper nozzle" of Qin et al. (2018). The "velocity inlet" was still used in this paper and had not been modified.
Point 9: Further, the inlet boundary condition is very close to the region of interest. In this case, special care has to be taken in order to avoid negative influences on the results provided by the boundary condition. This was not done by the authors.
Response 9: We are very sorry for our negligence of special care for boundary condition. Some specific details are supplemented in the paper.
Lines133-144: No slip boundary condition at the wall and standard wall function near the wall has been applied.
Lines153-157: To simulate the behavior of the steel-slag interface and turbulence inhibitor more accurately, local grid refinement technology was applied, and the meshes of the FLUENT computational domain included non-uniform grids with about 1500000 cells. Simultaneously, mesh refinement of the steel-slag interface and turbulence inhibitor were considered.
Point 10: Slag viscosity is strongly dependent on temperature. Is it valid to perform calculations of an isothermal model?
Response 10: During the steady continuous casting, the high temperature molten steel continuously enters the impact zone from the ladle shroud; the temperature of slag layer contacting with liquid steel is higher; and the thickness of liquid slag is generally more than 20 mm. The steel-slag interface studied in this paper is less than 20 mm. Therefore, it is reasonable to perform calculations of an isothermal model in this paper. References include (1) "Multiphase flow in a five-strand tundish using trumpet ladle shroud during steady-state casting and ladle change-over" of Zhang et al. (2018); (2) "Optimization of flow, heat transfer and inclusion removal behaviors in an odd multistrand bloom casting tundish" of Fang et al. (2020); (3) "Multiphase Flow Modeling of Slag Entrainment During Ladle Change-Over Operation" of Morales et al. (2016).
Point 11: I also have major concerns on the novelty and the impact of the work:
Response 11: The novelty and the impact of the work are as follows:
a) The test object is a six-strand continuous casting tundish with a nominal capacity of 66 ton in a Chinese special steel plant. The impact area and the casting area are connected by a flow channel with a certain slope. In recent years, the tundish with the large capacity high proportion of impact area is gradually used in some steel plants in China. It is necessary and meaningful to study the new structure tundish. The work is not only beneficial to optimize the flow control device and solve some practical problems encountered by the steel plant, but also may lead the upgrading of tundish structure.
b) At present, the research on the multiphase behavior of tundish mainly focused on the operation of ladle changing, argon blowing and steel filling and the research on the effect of turbulence inhibitor on the steel-slag flow have not been introduced into the multiphase simulation. The work focuses on the steel-slag interface fluctuation, which could be more closely related to the inspirations, spatter and slag entrainment of the jet flow.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.
We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.pdf
Reviewer 3 Report
Although the paper presents correctly the aim of the study and the associated results, it needs an extensive editing of English language and style. In particular, past is used through the whole paper, when 90% could (should) be written at present simple. This make the understanding quite difficult sometimes.
Other language mistakes can be found in the paper, I will not detail them here, and advise the authors to submit their proof to an English native.
Some other comments hereunder:
lines 38 to 42: "turbulence inhibitors could" may be suppressed 4 times
line 44: tundish structures are summarized...
line 61: which could be more closely
lines 69-70 : the comparison of sections
lines 88-89: please discuss the validity of your hypothesis (constant density)
line 91: interface was set to
line 96 : that the fluid flow
line 102: reference for k-eps model equations
line 108: unit for G
line 108: u is the velocity
line 109: µeff is the effective viscosity
line 115: Since a void (?) region
line 124: fluid flow
line 129: m.s-1 instead of m/s for the sake of homogeneity
line 144 : with such design
lines 156-158: please provide a sketch of the mesh that you use
line 164: the tracer masse fraction was set to 1
line 165: the tracer masse fraction was set to 0
line 168: numerical model at 800s (you write often in xxx s rather than at xxx seconds. I will not mention the next occurrenceq but please make the correction)
lines 174-175 : case1( case2) installed ==> ?
line 226 : the arithmetic mean
line 227: similarity factor
line 240: Figures 4 (a) are quite difficult to read due to small size
line 240: figure 4 (b), bottom : you use triangles instead of squares in the legend for the hydraulic model
line 272: difficult to conclude on the level of turbulence with k. Could you instead draw the turbulence intensity = µturb/µlam) ?
line 298: Vec (beginning of line) or Voc (end of line) for vorticity ?
line 310: inclusions are difficult to remove
line 318: cases present obvious differences
line 323: interface change
line 332: key points location (without ')
line 355: due to surface tension
Author Response
Response to Reviewer 3 Comments
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Effect of turbulence inhibitors on molten steel flow in 66 ton T-type tundish with large impact area” (ID: metals-883805). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to your comments are as flowing:
Lines 38 to 42: "Turbulence suppressor can" had been suppressed 4 times.
Line 43: The statements of “tundish structure summarized” were corrected as “tundish structures are summarized”.
Line 61: The statements of “which could more closely” were corrected as “The steel-slag interface fluctuation could be more closely”.
Lines 68-69: The statements of “The sections comparison of” were corrected as “The comparison of sections”.
Point 1: Lines 88-89: Please discuss the validity of your hypothesis (constant density)
Response 1: During the steady continuous casting, the tundish plays an important role to deliver molten steel from the ladle to the mold at constant flow rate, temperature, and composition. The change of temperature is not obvious in the tundish, which is less than 20 ℃. In the above temperature range, the density of molten steel changes little. The constant density can effectively simulate the actual situation. In recent years, "constant density" usually selected for the boundary condition. For example, (1) "Numerical simulation of transient multiphase flow in a five-strand bloom tundish during ladle change" of Zhang et al. (2018); (2) "Removal mechanism of microscale non-metallic inclusions in a tundish with multi-hole-double-baffles" of Jin et al. (2018); (3) "A simulation study on the flow behavior of liquid steel in tundish with annular argon blowing in the upper nozzle" of Qin et al. (2018). The "constant density" was still used in this paper and had not been modified.
Line 91: The statements of “interface was” were corrected as “interface is set to”.
Line 96: The statements of “that the flow of fluid” were corrected as “that the fluid flow”.
Point 2: Line 102: reference for k-eps model equations.
Response 2: References had been added.
Line 108: “unit for G” was added.
Line 108: The statements of “ ” were corrected as “u”.
Line 109: The statements of “ ” were corrected as “ ”.
Line 115: The statements of “Since avoid region” were corrected as “Since a void region”.
Line 124: The statements of “flow of fluid” were corrected as “fluid flow”.
Line 129: The statements of “m/s” were corrected as “m·s-1”.
Line 144: The statements of “with such designation” were corrected as “with such design”.
Point 3: Lines 156-158: please provide a sketch of the mesh that you use.
Response 3: Mesh-independence study draws lessons from the paper "Numerical simulation of transient multiphase flow in a five-strand bloom tundish during ladle change" of Zhang et al. (2018). The study was the most basic and without novelty, so the author thinks that it is not necessary to provide a sketch of the mesh.
Line 166: The statements of “the tracer mass fraction was set 1” were corrected as “the tracer mass fraction was set to 1”.
Line 166: The statements of “the tracer mass fraction was set 0” were corrected as “the tracer mass fraction was set to 0”.
Line 170: The statements of “numerical model in 800s” were corrected as “numerical model at 800s”.
Lines 176-177: The statements of “case1 (case2)” were corrected as “case 1 (case 2)”.
Line 228: The statements of “arithmetic meaning value” were corrected as arithmetic mean value”.
Line 229: The statements of “similarity” were corrected as “similarity factor”.
Point 4: Line 240: Figures 4 (a) is quite difficult to read due to small size. Line 240: figure 4 (b), bottom: you use triangles instead of squares in the legend for the hydraulic model.
Response 4: We are very sorry for our incorrect writing. The quality of figure 5 had been improved and triangles had replaced squares in the legend for the hydraulic model.
Point 5: Line 272: difficult to conclude on the level of turbulence with k. Could you instead draw the turbulence intensity =µturb/µlam)?
Response 5: The results of turbulence study showed that the turbulence inhibitor had obvious effect and the turbulent kinetic energy at the steel-slag interface decreased to about 20% of the initial value. The authors believe that the contours and values can better reflect the simulation results. Lines 282-283: “The effect of turbulence inhibitor on dissipation of turbulent kinetic energy was obvious” was added.
Line 297: The statements of “The vorticity is one of” were corrected as “The velocity is one of”.
Line 311: The statements of “inclusion is difficult to remove” were corrected as “inclusions are difficult to remove”.
Line 318: The statements of “cases had obvious differences” were corrected as “cases present obvious differences”.
Line 324: The statements of “interface changed” were corrected as “interface change”.
Line 333: The statements of “key points’ location” were corrected as “key points location”.
Line 356: The statements of “due surface tension” were corrected as “due to surface tension”
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.
We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Paper is ready for publication
