document: In this paper, however, we prefer the simpler ‘framed’ cell employed by Hadjiconstantinou and Patera [16], where the shear stress is generated by constraining the velocity in a ‘frame’ rather than by modifying the shape of the box. The framed cell is periodic, but we cannot simply calculate the average stress in the whole box because the presence of an external buffer would produce spurious results. We need the local stress in the core region, but this complicates the Oij term in Eq. (3). There are other methods to calculate the stress tensor such as the method of planes [32], the volume-average approach [26,14], or the method derived from the Schweitz virial relation [25], but, in general, we must choose between a complicated computational cell (i.e. Lees–Edwards cell) and simplifying the calculation of the momentum flux, or a simple cell (i.e. framed cell) and complicating the calculation of the momentum flux. The new method we propose here does not need the direct calculation of the flux, so it avoids this issue altogether: we can use the framed cell and, at the same time, avoid the calculation of the IK equation.
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