Circular Basin: Difference between revisions

From CIRPwiki
Jump to navigation Jump to search
No edit summary
 
(13 intermediate revisions by 2 users not shown)
Line 3: Line 3:
=Problem=
=Problem=
Dupont (2001) presented an analytical solution for a closed circular domain on an f-plane with a linear bottom friction. The governing equations are
Dupont (2001) presented an analytical solution for a closed circular domain on an f-plane with a linear bottom friction. The governing equations are
  {{Equation| <math> \frac{\partial H U}{\partial x} + \frac{\partial H V}{\partial y} = 0 </math>|2=1}}
{{Equation|<math>
  {{Equation| <math> -f_c V + g \frac{\partial \eta}{\partial x} =  \kappa U + \frac{W y}{R H} </math>|2=2}}
  \frac{\partial H U}{\partial x} + \frac{\partial H V}{\partial y} = 0
  {{Equation| <math> f_c U + g \frac{\partial \eta}{\partial y} =  \kappa V </math>|2=3}}
</math>|1}}
 
{{Equation|<math>
-f_c V + g \frac{\partial \eta}{\partial x} =  \kappa U + \frac{W y}{R H}
</math>|2}}
 
{{Equation|<math>
f_c U + g \frac{\partial \eta}{\partial y} =  \kappa V
</math>|3}}


where <math>U</math> and <math>V</math> are the depth-averaged current velocities in the <math>x</math> and <math>y</math> directions respectively, <math>g</math> is the gravitational constant, <math>\eta</math> is the water surface elevation with respect to mean sea level, <math>\kappa</math> is a linear bottom friction coefficient, <math>R</math> is the radius of the domain, <math>H</math> is the water depth, and <math>W</math> is a constant equal to the gradient of the wind forcing.
where <math>U</math> and <math>V</math> are the depth-averaged current velocities in the <math>x</math> and <math>y</math> directions respectively, <math>g</math> is the gravitational constant, <math>\eta</math> is the water surface elevation with respect to mean sea level, <math>\kappa</math> is a linear bottom friction coefficient, <math>R</math> is the radius of the domain, <math>H</math> is the water depth, and <math>W</math> is a constant equal to the gradient of the wind forcing.
Line 11: Line 19:
=Solution=
=Solution=
The analytical solution for water surface elevation solution is given by  
The analytical solution for water surface elevation solution is given by  
{{Equation| <math> \eta =  
{{Equation|<math>
\begin{cases}  
\eta =  
\frac{W{{r}^{2}}\sin 2\theta }{4gHR}, & \mbox{if } f_c=0  \\  
  \begin{cases}  
\frac{W{{f}_{c}}}{RgH\kappa }\left[ \frac{{{R}^{2}}}{8}+\frac{{{r}^{2}}}{4}\left( \frac{\kappa }{{{f}_{c}}}\sin 2\theta -1 \right) \right], & \mbox{if } f_c \ne0 \\
  \frac{W{{r}^{2}}\sin 2\theta }{4gHR}, & \mbox{if } f_c=0  \\  
\end{cases} </math> |2=1}}
  \frac{W{{f}_{c}}}{RgH\kappa }\left[ \frac{{{R}^{2}}}{8}+\frac{{{r}^{2}}}{4}\left( \frac{\kappa }{{{f}_{c}}}\sin 2\theta -1 \right) \right], & \mbox{if } f_c \ne0 \\
  \end{cases}
</math>|4}}


The current velocities are independent of the Coriolis parameter and are given by  
The current velocities are independent of the Coriolis parameter and are given by  
{{Equation| <math> U = \frac{W y }{2 R H \kappa} </math> |2=3}}
{{Equation|<math>
{{Equation| <math> V = -\frac{W x }{2 R H \kappa} </math> |2=4}}
U = \frac{W y }{2 R H \kappa}  
</math>|5}}
 
{{Equation|<math>
V = -\frac{W x }{2 R H \kappa}
</math>|6}}


= Setup =
= Setup =
Line 25: Line 40:
The model is run to steady state from zero current and water level initial conditions with <math> W = 10^-4 \text{m}^2 \text{s}^{-2} </math>, <math> \kappa = 10^{-3} \text{s}^{-1} </math> , and <math> f_c = 0</math>. Table 1 shows the general settings used for CMS-Flow. Figure 1 shows the computational grid with 5 levels of refinement from 2000 m to 125 m.
The model is run to steady state from zero current and water level initial conditions with <math> W = 10^-4 \text{m}^2 \text{s}^{-2} </math>, <math> \kappa = 10^{-3} \text{s}^{-1} </math> , and <math> f_c = 0</math>. Table 1 shows the general settings used for CMS-Flow. Figure 1 shows the computational grid with 5 levels of refinement from 2000 m to 125 m.


<br style="clear:both" />
'''Table 1. General Settings for Wind-driven flow in a circular basin'''
'''Table 1. General Settings for Wind-driven flow in a circular basin'''
{|border="1"
{|border="1"
Line 36: Line 51:
|Ramp Period || 24 hrs
|Ramp Period || 24 hrs
|-
|-
|Initial Water Depth || 10 m
|Initial Water Depth || 100 m
|-
|-
|Mixing Terms || Off
|Mixing Terms || Off
Line 47: Line 62:
   
   
<br style="clear:both" />
<br style="clear:both" />
= Results =
= Results =
[[Image:CB3_Analytical_No_Coriolis_V4.png|thumb|left|800px| Figure 1. Analytical current velocities and water levels.]][[Image:CB3_Calculated_No_Coriolis_V4.png|thumb|right|800px| Figure 1. Calculated current velocities and water levels.]]
== No Coriolis ==
[[Image:CB3_Analytical_No_Coriolis_V4.png|thumb|left|600px| Figure 1. Analytical current velocities and water levels for the case without Coriolis.]]
[[Image:CB3_Calculated_No_Coriolis_V5.png|thumb|right|600px| Figure 2. Calculated current velocities and water levels for the case without Coriolis.]]


[[Image:CB3_Analytical_Coriolis_V4.png|thumb|left|800px| Figure 1. Analytical current velocities and water  levels.]][[Image:CB3_Calculated_Coriolis_V4.png|thumb|right|800px| Figure 1. Calculated current velocities and water levels.]]
<br style="clear:both" />
'''Table 2. Goodness of fit statistics for the current velocity and water level.'''
{|border="1"
|'''Variable''' ||'''NRMSE, %'''||'''NMAE, %'''||'''R^2'''||'''Bias'''
|-
|U-Velocity || 2.52 || 0.37 || 0.999 || -8.5e-8 m/s
|-
|V-Velocity || 2.53 || 0.38 || 0.999 || 7.26e-8 m/s
|-
|Water Level|| 0.03 || 0.02 || 0.999 || -3.5e-7 m
|}
* For a definition of the goodness of fit statistics see [[Statistics |  Goodness of fit statistics]].


<br style="clear:both" />
<br style="clear:both" />


Table 2. Goodness of fit statistics for the current velocity and water level
== With Coriolis ==
[[Image:CB3_Analytical_Coriolis_V4.png|thumb|left|600px| Figure 3.  Analytical current velocities and water  levels for the case with Coriolis.]]
[[Image:CB3_Calculated_Coriolis_V5.png|thumb|right|600px| Figure 4. Calculated current velocities and water levels for the case with Coriolis.]]
 
<br style="clear:both" />
'''Table 3. Goodness of fit statistics for the current velocity and water level.'''
{|border="1"
{|border="1"
|'''Variable''' ||'''RRMSE, %'''||'''RMAE, %'''||'''R^2'''||'''Bias'''
|'''Variable''' ||'''RRMSE, %'''||'''RMAE, %'''||'''R^2'''||'''Bias'''
|-
|-
|U-Velocity || 3.88 || 0.64 || 0.997 || -4.06e-5
|U-Velocity || 2.53 || 0.37 || 0.999 || -8.5e-8 m/s
|-
|-
|V-Velocity || 3.87 || 0.64 || 0.997 || 4.06e-5
|V-Velocity || 2.56 || 0.37 || 0.999 || 6.5e-8 m/s
|-
|-
|Water Level|| 0.16 || 0.13 || 1.000 || -3.56e-6
|Water Level|| 0.03 || 0.02 || 0.999 || -3.0e-7 m
|}
|}
<br style="clear:both" />


= References =
= References =

Latest revision as of 20:07, 18 April 2013

UNDER CONSTRUCTION

Problem

Dupont (2001) presented an analytical solution for a closed circular domain on an f-plane with a linear bottom friction. The governing equations are

  (1)
  (2)
  (3)

where and are the depth-averaged current velocities in the and directions respectively, is the gravitational constant, is the water surface elevation with respect to mean sea level, is a linear bottom friction coefficient, is the radius of the domain, is the water depth, and is a constant equal to the gradient of the wind forcing.

Solution

The analytical solution for water surface elevation solution is given by

  (4)

The current velocities are independent of the Coriolis parameter and are given by

  (5)
  (6)

Setup

Figure 1. Computational grid.

The model is run to steady state from zero current and water level initial conditions with , , and . Table 1 shows the general settings used for CMS-Flow. Figure 1 shows the computational grid with 5 levels of refinement from 2000 m to 125 m.


Table 1. General Settings for Wind-driven flow in a circular basin

Parameter Value
Time step 3600 s
Simulation Duration 72 hrs
Ramp Period 24 hrs
Initial Water Depth 100 m
Mixing Terms Off
Wall Friction Off
Linear Bottom Friction Coefficient 0.001



Results

No Coriolis

Figure 1. Analytical current velocities and water levels for the case without Coriolis.
Figure 2. Calculated current velocities and water levels for the case without Coriolis.


Table 2. Goodness of fit statistics for the current velocity and water level.

Variable NRMSE, % NMAE, % R^2 Bias
U-Velocity 2.52 0.37 0.999 -8.5e-8 m/s
V-Velocity 2.53 0.38 0.999 7.26e-8 m/s
Water Level 0.03 0.02 0.999 -3.5e-7 m


With Coriolis

Figure 3. Analytical current velocities and water levels for the case with Coriolis.
Figure 4. Calculated current velocities and water levels for the case with Coriolis.


Table 3. Goodness of fit statistics for the current velocity and water level.

Variable RRMSE, % RMAE, % R^2 Bias
U-Velocity 2.53 0.37 0.999 -8.5e-8 m/s
V-Velocity 2.56 0.37 0.999 6.5e-8 m/s
Water Level 0.03 0.02 0.999 -3.0e-7 m


References

  • Dupont, F., 2001. Comparison of numerical methods for modelling ocean circulation in basins with irregular coasts. Ph.D. thesis, McGill University, Montreal.

Test Cases

Documentation Portal