Measurement of Physical Properties of Sorghum Seeds and Calibration of Discrete Element Modeling Parameters

Round 1

Reviewer 1 Report

Manuscript concerns physical measurements of physical properties of sorghum seeds and calibration of DEM simulations parameters of seeds. The basic physical parameters of seeds (size distribution, elastic modulus and Poisson’s ratio) and contact parameters (coefficients of friction and restitution coefficient) were measured and next repeated in DEM simulations. The contact parameters were determined as the best fitting DEM simulation of the measured angle of repose. Manuscript provides some limited new information useful for DEM modeling of mechanical behavior of sorghum seeds. It is in scope of journal. 

Particular comments:

1. Lines 123-124. “ratio of the velocities before and after the collision“. Please be more specific. The coefficient of restitution is the ratio of the velocity after collision to the velocity before collision.
2. Eq. (7) is wrong. h/H > 1, and sqr(h/H) > 1.
3. Why two different tests were arranged for determination of the coefficient of restitution of seed-seed collision (inclined surface) and seed-smooth surface collision (horizontal surface)?
4. Fig. 7. How did you recognize sliding from rolling of individual particle on inclined surface? I have doubt on physical sense of this experiment as rolling and sliding of a single particle is very difficult to be recognized.
5. Section 3. Results and discussion. A lot of similar studies have been published recently for different seeds. Authors did not provided any discussion and comparison of their own results with results of similar studies presented in literature.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This is interesting research to combine the experimental results with DEM modeling by validating the results. However, some improvements according to the DEM modeling should be taken into consideration. 

1) The modeling methodology for the sorghum seeds should be added to the research method, especially contact modeling (which contact model used), Check this reference (El-Emam, Mahmoud A, Ling Zhou, Weidong Shi, Chen Han, Ling Bai, and Ramesh Agarwal. 2021. “Theories and Applications of CFD – DEM Coupling Approach for Granular Flow : A Review.” Archives of Computational Methods in Engineering. https://doi.org/10.1007/s11831-021-09568-9.

2) Why do the authors use the multi-sphere modeling of the seed particle, there is another new technique about particle modeling that can model the whole particle as a true shape modeling that can give more reliable and trusted results.

Author Response

请参阅附件。

Author Response File: Author Response.docx

Reviewer 3 Report

Several physical experiments, together with DEM simulations, are carried out to determine the physical properties of sorghum seeds and their contacting parameters for particle-particle and particle-wall interactions. Correlations to predict these parameters are also given. The capability of these treatments look quite fine when using them to perform a real DEM simulation. The work can be of interest of researchers in agriculture and the manuscript is overall well organized.

1. It seems that obtained parameters can be somehow sensitive to the state of the sorghum seeds, like shape, size and moisture content. The findings in this paper are thus very limited for those readers who worked on other agriculture particles or other sorghum seeds. Any comments for them? Or they should do entirely the same thing like the authors did in the current work to obtain their contact parameters.
2. Parentheses are absent in Eq. 5. The number of spheres in Figure 12 may also have influence on the numerical results.
3. Is it possible to compare the numerical results in Section 2.6 with corresponding experimental results?
4. Since the parameters for particle-particle in Table 4 were not calibrated separately as those for particle-wall, even with central composite design experiment. Deeper discussion can be made to further highlight the role or effect of X4, X5 and X6 (which one is more dominative?).
5. Is there a way to obtain the particle-particle collision parameters, one by one, just following the similar logic in Section 2.6? Say, to use the interaction between two particles to obtain the Collision Restitution Coefficient, and others.
6. At last, as introduced in P1, the innovation of the current work can be limited for other particle materials. The validation work is fine but really likes a half of a completed work with the latter part missing. The latter part can be discussion on the effects of operation parameters in an actual engineering process. At least, optimal ones are obtained.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Corrections are acceptable.

Reviewer 3 Report

Responses are fine and the manuscript is revised accordingly. A nice paper overall and thus recommending it publication now.