This study examined the coefficient of friction μ_r between rice grains and an abrasive roll in order to develop a rice milling model applicable to analyzing rice milling mechanisms in sake brewing. Using a discrete element method as a basis for model development, CAD data were applied to model a horizontal-type test milling machine, and 3D scanning data for brown rice grains were used to create models for brown rice as well as for rice milled down to 90 %, 80 %, and 70 % milling yields. Taking Δd to be the distance between the centroids in the grain size distribution for both the experimental and calculation results, the μ_r value was examined for each rice milling yield according to the value of Δd. The results revealed that it was possible to produce favorable grain flow conditions by setting μ_r to 0.725, 0.75, 0.95, and 0.95 for brown rice and 90 %, 80 %, and 70 % milled rice, respectively.

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