Eddy Viscosity

From CIRPwiki
Revision as of 20:02, 18 July 2014 by Rdchldlj (talk | contribs)
Jump to navigation Jump to search

The term eddy viscosity arises from the fact that small-scale vortices or eddies on the order of the grid cell size are not resolved and only the large-scale flow is simulated. The eddy viscosity is intended to simulate the dissipation of energy at smaller scales than the model can simulate. In the nearshore environment, large mixing or turbulence occurs due to waves, wind, bottom shear, and strong horizontal gradients; and therefore the eddy viscosity is an important aspect which can have a large influence on the calculated flow field and resulting sediment transport. In CMS-Flow, the total eddy viscosity, νt , is equal to the sum of three parts: 1) a base value ν0, 2) the current-related eddy viscosity νc, and 3) the wave-related eddy viscosity νw and is defined as,

(2-21)

The base value (ν0) is approximately equal to the kinematic eddy viscosity (~1×10-6 m2/s), but may be changed by user. The other two components (νc and νw) are described in the sections below.