Simulation of Granular Organic Fertilizer Application by Centrifugal Spreader

Round 1

Reviewer 1 Report

Round 1:

The entire publication is written correctly. It would be nice to add the main results in the conclusions.

In references, the font for the year of publication should be in bold.

In the abstract on line 14-15 I highlighted a repetition of the term "fertilizer".
36-38 it would take a source for this statement.
51 the beginning of the sentence (In fact, geo-referenced soil sampling or, better, measurement of soil parameters) is misleading and little is understood, perhaps it needs to be reformulated.
figure 2: to increase the size and in the caption explain better what you are looking at.
142 for the initials IGS at least specify what it means, even if only in brackets, given that for the other acronyms it has been done.
Figure 4, in b the numbers at the top are not read, they are cut, moreover, they represent two different types of fertilizers, and are reproduced however in two different perspectives, making it difficult to understand the actual differences, it should be changed or justified in the caption because they were choices these two perspectives (essentially what did they want to show?)

Round 2:

I accept revisied version.

Author Response

We would like to thank for the review of our manuscript.  

Reviewer 2 Report

Round 1

The paper written by Raimonda Zinkevičienė et al. deals with the simulation of the spreading of particles by means of discrete element methods.

Although the subject studied is interesting (optimization of a process) the paper is unclear and the writing not rigorous. As a reader, I was unable to find all the information necessary to reproduce the authors' work.  Consequently I can't recommend publication.

In more details

1. The goal of the paper seems to be a « proof of concept ». Is it enough to deserve publication in a scientific journal ? It is indeed well known that DEM can be used to simulate much more complex systems.
2. I did not understand how the effect of the air was taken into account. I want a precise answer.
3. I did not understand what the travelled distance is and how it is computed. Written "The distance travelled by the fertilizer particles was evaluated by relying on the rotation speed of the spinning discs during the tests. The weight of the granules was also taken into account." is clearly not enough.
4. The quality of ALL the plots is poor. Use bigger fonts! Make you plot attractive! Figure 2 is just awful (what are the illegible numbers?). The same for figure 2 (look at your color maps!) .
5. What are the parameters used to the contact forces (particle-particle and particle-spreader). The authors wrote "The default values of Hertz-Mindlin contact for the non-slip model, that is in EDEM software, was used for the simulation analysis." Do they mean the reader has to learn how to use edem to understand their work? What do they mean by non-slip? Do they mean Infinite friction coefficient?
6. Some relevant literature is missing for example the works of Rioual (e.g. doi :10.1063/1.2424647 among others). Note that the referee is not involved in the authorship of these papers.

Round 2

Unfortunately, the authors did not really address my comments and modified their MS in clumsy way. More precisely

1. The presented study is still a proof of concept. The authors modify their introduction… but neither their results nor their analysis! The presented are somewhat obvious.
2. I still do not understand how the effect of air is taken into account. Do the authors use a force to model the effect of the air? If so, what force (give the equations!)? Similarly the choice of the forces used (and the corresponding parameters) is still unclear and not justified. Please write down the equations used in the simulation for all the forces. If the authors used the “Default values” please give their values. Do the authors really know how DEM work or did they just use EDEM as a black box?
3. I still have difficulties with the travelled distance. In figures 3 and 4, please explain what t=0 refers to. Also what are the symbols (e.g. red square or green triangle located at t=0). Finally, is it correct to say that it t tends towards large values; the travelled distance will reach a constant value? If I am right the simulations should be run for longer times. If not, please explain.
4. Why the authors do removed fig 2? I did not request to remove it. Now we even do not know what the shape of the grains used in DEM is!

In conclusion, I cannot recommend the present MS and recommend rejection. To me, the description level is so low that it is impossible to reproduce the reported results. We do not know the shape of the grains, we do not know in details which forces are used and what is measured is unclear. The analysis of the results is also weak.

Round 3

The authors made significant efforts to address my comments. To me the manuscript is still far from being perfect, but is close to be accepatable for publication. I only recommand to the authirs to write the equations used to compute grain-grain interaction (writing Hertz-midlin is not enough) including for rolling friction.

Author Response

We would like to thank for the review of our manuscript. All answers to the reviewer comments are in the fille.