**A method for coarse graining fluctuation velocities in granular flows**

NS Ray and D Khakhar, GRANULAR MATTER, 25, 46 (2023).

DOI: 10.1007/s10035-023-01338-7

The granular temperature, which is the mean kinetic energy per unit mass of velocity fluctuations, is an important rheological parameter for granular flows. Artoni and Richard (Phys Rev E 91: 032202, 2015) showed that accurate calculation of the fluctuation velocity during coarse graining requires the subtraction of the mean velocity at the position of the particle since the variation of the mean velocity over the coarse graining domain may be of the same order as the fluctuation velocity. This requires a two-step calculation. In this study, a single-step method of calculating granular temperatures is proposed. The values obtained by this method for a simulated system of inclined surface flow of granular materials are compared with those obtained using earlier methods and are shown to be accurate.

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