Calibration and Testing of Discrete Element Simulation Parameters for Urea Particles

Round 1

Reviewer 1 Report

1) How are the equations (2) and (3) obtained and what does the constant 0.338 mean in Eq. (2)? Please explain.
2) I think, for readers' convenience, Poisson's ratio and modulus of elasticity could be included in Table 1.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Reviewer’s comment on manuscript processes-1609617

The manuscript entitled "Calibration and testing of discrete element simulation parameters for urea particles” by Haoran Bu et al. is devoted to determination of the basic physical parameters of urea granular fertilizer. Authors determined the particle size, thousand particle mass, density, modulus of elasticity, Poisson's ratio, coefficient of static and rolling friction and angle of repose. These parameters affect strongly the work of the fertilizer application devices and some of them are input parameters for DEM simulations. Simulation parameters were calibrated by combining physical and simulation tests, providing a set of parameters that could be next used to model process of fertilizer discharging. This study provided a valuable set of parameters that may be also used for modelling different processes involving fertilizers. The topic of manuscript is interesting and paper is well organized. The novelty and the significance of the study is pointed out. The outcome of the research study are interesting and may find application in designing fertilizer application devices.  I recommend the publication of the manuscript on the Processes provided that the following suggestions will be taken into account and shortcomings will be removed:

 

Line 222: “The test will be different materials attached to the test panel of the inclinometer.”- Please, reedit that sentence.

Lines 402-411: The text in these lines is a repetition of text in lines 373-380. I suggest to reedit the text, give more general conclusions to avoid repetition.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The authors present a calibration procedure of the urea particles for use with a non-cohesive Hertz-Mindlin contact model via the commercial DEM solver EDEM. From a scientific point of view, the paper does not contribute any new findings or methods. It is a set of calibrated input data for material-specific simulations in EDEM. The authors use basic, commonly used calibration experiments to determine the DEM input data. The manuscript is in my opinion acceptable to Processes, but some major and minor revisions should be made.

Since the manuscript focuses only on a simple calibration of a single material, this calibration should be done in even greater detail. The packing test is missing (https://doi.org/10.3390/pr8020222). Bulk density versus particle bed volume versus friction parameters should be mentioned.

Why wasn't a simple vertical drop test used to measure spherical particles? Is the measurement methodology used an original contribution of the authors or was it adopted? With what accuracy were the reflections and particle trajectories determined? How was the particle-particle restitution coefficient measured? This is complicated for small spherical particles. The use of a double pendulum (https://doi.org/10.1016/j.cherd.2018.05.016) is suggested here.

The measurement methodology of sliding friction should be better described. How was the particle-particle friction measurement accounted for the particle shape and waveness factor of glued spheres at 150 mm stroke? Was a normal load applied during the measurement? Figure 6 should have a better telling value.

How was the particle-particle rolling friction coefficient determined?

Throughout the manuscript, PVC is used as the contact material. What if readers want to use steel or any different wall material. How will the behaviour of the virtual material differ. What will be the error?

The authors used an experimentally determined value for the shear modulus. Reducing its value is a common DEM practice. Did the authors consider calibrating with a lower shear modulus value to save computational cost?

Why was material discharge using a rotary feeder chosen as the calibration experiment? Free discharge from the hopper may provide better information on material behaviour (discharge time, mass flow rate, flow profiles, etc.)?

line 245 - temperature cannot be seen in figure 5

line 106 - All 1000 particles were measured manually with a calliper?

line 265 - How was the sphericity determined by manual calliper measurement?

line 269 - Why was a 3D CAD STL model imported to create the spherical particle? Was the model artificially created or taken by 3D scanning? Or was it not an exact sphere and multiple sub-particles were used? How many? This is not apparent from Figure 9b.

Line 282 - How was the repose angle from the DEM simulations evaluated? Graphically, by exporting coordinates, or was some script used using the API?

Since the input data set for the EDEM model is the main output of the paper, I would expect Table 5 to be more towards the end.

Some odd terminology and typos occur in the text, e.g.:

- pumping plate method (line 244)

- missing spacing (lines 245, 246, Table 5)

- typos in chapters naming (lines 304, 311)

- degree should be in °... width should be used for the unit in mm (lines 374, 376, 379)

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors made the requested changes to the manuscript and answered the questions raised. I recommend the manuscript for publication.