CMS-Flow Eddy Viscosity
Jump to navigation
Jump to search
Overview
Turbulent diffusion is calculated in CMS using the eddy viscosity concept. The eddy viscosity is not a user definable parameter. The diffusion or Mixing terms of the momentum and transport equations may be turned off in the Flow tab of the CMS-Flow Model Control window. The CMS card used to turn On or Off the mixing terms is described in the Table below.
Table 1. CMS card used to turn On or Off the mixing terms in the momentum and transport equations
| Card | Arguments | Default | Typical Range | Description | Versions |
|---|---|---|---|---|---|
| USE_MIXING_TERMS | CHARACTER | ON | ON |OFF | Turns On and Off the mixing terms in the momentum and transport equations. Essentially sets the eddy viscosity and mixing coefficients to zero. | >=3.5 |
Turbulence Models and Coefficients (Advanced)
A description of the advanced cards related to eddy viscosity is shown in the table below.
| Card | Arguments | Default | Typical Range | Description | Versions |
|---|---|---|---|---|---|
| TURBULENCE_MODEL | CHARACTER | SUBGRID | SUBGRID |FALCONER| PARABOLIC | MIXING-LENGTH | Specifies the turbulence model used | >=3.5 |
| EDDY_VISCOSITY_CONSTANT | REAL | 1.0E-6 | >=0.0 | Constant contribution or base value of eddy viscosity | >=3.5 |
| EDDY_VISCOSITY_BOTTOM | REAL | 0.0667 | 0.02-0.1 | Coefficient related to the contribution to eddy viscosity from the bottom shear | >=3.5 |
| EDDY_VISCOSITY_HORIZONTAL | REAL | 0.4 | 0.1-0.2 | Coefficient related to the contribution to eddy viscosity from horizontal velocity gradients | >=3.5 |
| EDDY_VISCOSITY_WAVE | REAL | 0.5 | 0.2-1.0 | Coefficient related to the wave bottom friction contribution to eddy viscosity | >=4.0 |
| EDDY_VISCOSITY_BREAKING | REAL | 0.05 | 0.05-0.1 | Coefficient related to the wave breaking contribution to eddy viscosity | >=4.0 |
More information can be found here.