CMS-Flow Eddy Viscosity: Difference between revisions
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= Overview = | |||
[[image:Mixing_Terms.png|thumb|right|500px| Figure 1. Toggle for turning ''On'' and ''Off'' the mixing terms in the SMS 11.0 interface.]] | |||
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''' | |||
{| border="1" | |||
! Card !! Arguments !! Default !! Typical Range !! Description !! Versions | |||
|- | |||
|USE_MIXING_TERMS || CHARACTER|| ON || ON <nowiki>|</nowiki>OFF || Turns On and Off the mixing terms in the momentum and transport equations. || >=3.5 | |||
|} | |||
<br style="clear:both" /> | |||
= Turbulence Models (Advanced) = | |||
Due to the large amount of turbulence in the surf zone, the nearshore eddy viscosity and resulting mixing terms can be quite large making the flow sensitive to the eddy viscosity formulation implemented. | |||
A description of the advanced cards related to eddy viscosity is shown in the table below. | |||
<br style="clear:both" /> | <br style="clear:both" /> | ||
{| border="1" | {| border="1" | ||
! Card !! Arguments !! Default !! Typical Range !! Description !! Versions | ! Card !! Arguments !! Default !! Typical Range !! Description !! Versions | ||
|- | |- | ||
|TURBULENCE_MODEL || CHARACTER|| SUBGRID || SUBGRID <nowiki>|</nowiki>FALCONER<nowiki>| </nowiki>PARABOLIC <nowiki>| </nowiki>MIXING-LENGTH || Specifies the turbulence model used || >=3.5 | | TURBULENCE_MODEL || CHARACTER|| SUBGRID || SUBGRID <nowiki>|</nowiki>FALCONER<nowiki>| </nowiki>PARABOLIC <nowiki>| </nowiki>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_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_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_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_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 | | 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 [[CMS-Flow:Eddy Viscosity|'''here''']]. | More information can be found [[CMS-Flow:Eddy Viscosity|'''here''']]. | ||
=Notes= | |||
=Example= | |||
---- | ---- | ||
[[CMS#Documentation Portal | Documentation Portal]] | [[CMS#Documentation Portal | Documentation Portal]] | ||
Latest revision as of 21:56, 8 September 2011
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. | >=3.5 |
Turbulence Models (Advanced)
Due to the large amount of turbulence in the surf zone, the nearshore eddy viscosity and resulting mixing terms can be quite large making the flow sensitive to the eddy viscosity formulation implemented.
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.