Shear and Bulk Acceleration Viscosities in Simple Fluids

Inhomogeneities in the velocity field of a moving fluid are dampened by the inherent viscous behavior of the system. Both bulk and shear effects, related to the divergence and the curl of the velocity field, are relevant. On molecular time scales, beyond the Navier-Stokes description, memory plays an important role. Using molecular and overdamped Brownian dynamics many-body simulations, we demonstrate that analogous viscous effects act on the acceleration field. This acceleration viscous behavior is associated with the divergence and the curl of the acceleration field, and it can be quantitatively described using simple exponentially decaying memory kernels. The simultaneous use of velocity and acceleration fields enables the description of fast dynamics on molecular scales.

Automated summary

The velocity field in a moving fluid is affected by its inherent viscous behavior, which helps to dampen any inhomogeneities. Both bulk and shear effects, related to the divergence and curl of the velocity field, play a role in this process. Memory also plays a significant role on molecular time scales beyond the Navier-Stokes description. Through molecular and overdamped Brownian dynamics many-body simulations, it has been demonstrated that similar viscous effects also act on the acceleration field, which can be quantitatively described using simple exponentially decaying memory kernels. The simultaneous use of velocity and acceleration fields allows for the description of fast dynamics on molecular scales.