Optimum viscosity reduction by cruising in dense suspensions.

Dense suspensions tend to shear jam at large packing fractions. However, it has recently been shown that various oscillation

protocols can reduce viscosity and dissipation. Furthermore, oscillations can even unjam shear-jammed suspensions. In this numerical

work, we ask ourselves what is the optimum shear protocol in terms of dissipation. We show that the cruising protocol is better than an

oscillatory shear applied in the perpendicular direction, even though the latter's viscosity reduction is more considerable. Ultimately, we

give a simple geometrical interpretation of this counter-intuitive decoupling of minima of viscosity and dissipation for the cruising protocol.

This work paves the way for a new class of highly-energy efficient shear/mass-transport protocol.