CMS-Flow:Bottom Friction: Difference between revisions

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where <math> lambda_{wc} </math> is the nonlinear wave enhancement factor which varies depending on the model selected. There are five models available in CMS:
where <math> lambda_{wc} </math> is the nonlinear wave enhancement factor which varies depending on the model selected. There are five models available in CMS:
1. Simplified quadratic formula
1. Simplified quadratic formula (named W09 in CMS)
2. Soulsby (1995) Data2 Method
2. Soulsby (1995) Data2 (named DATA2 in CMS)
3. Soulsby (1995) Data13 Method
3. Soulsby (1995) Data13 (named DATA13 in CMS)
4. Fredsoe (1984) Model
4. Fredsoe (1984) (names F84 in CMS)
5. Huynh-Thanh and Temperville (1991) Model
5. Huynh-Thanh and Temperville (1991) (named HT91 in CMS)


In this case the simplified expression for the combined wave and current mean shear stress is given by
In this case the simplified expression for the combined wave and current mean shear stress is given by
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</math>.
</math>.


       <math> \lambda_{wc} = 1 + bX^p(1-X)^q, with X=\frac{\tau_w}{tau_c + tau_w}  </math>
       <math> \lambda_{wc} = 1 + bX^p(1-X)^q, with X=\frac{\tau_w}{\tau_c + \tau_w}  </math>
 
where the coefficients <math>b</math>, <math>p</math>, and <math>q</math> depend on the model selected.
 
The default model is the simplified quadratic formula, but the user may change the model by using the advanced card
 
    WAVE-CURRENT_MEAN_STRESS      W09  !W09 | DATA2 | DATA13 | F84 | HT91

Revision as of 19:41, 5 May 2010

Bottom Friction

Flow without Waves

In the situation without waves, the bottom shear stress is calculated based on the quadratic formula

     

where is the bottom friction coefficient, is the depth-averaged current velocity.

Flow with Waves

In the case with waves, the bottom friction is calculated with the generalized formula

     

where is the nonlinear wave enhancement factor which varies depending on the model selected. There are five models available in CMS: 1. Simplified quadratic formula (named W09 in CMS) 2. Soulsby (1995) Data2 (named DATA2 in CMS) 3. Soulsby (1995) Data13 (named DATA13 in CMS) 4. Fredsoe (1984) (names F84 in CMS) 5. Huynh-Thanh and Temperville (1991) (named HT91 in CMS)

In this case the simplified expression for the combined wave and current mean shear stress is given by

     

For all of the other models, the general parameterization of Soulsby (1995) is used to calculate .

     

where the coefficients , , and depend on the model selected.

The default model is the simplified quadratic formula, but the user may change the model by using the advanced card

    WAVE-CURRENT_MEAN_STRESS       W09  !W09 | DATA2 | DATA13 | F84 | HT91