Difference between revisions of "Two Identical Submerged Docks using Symmetry"

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= Introduction =
+
{{complete pages}}
  
This is the finite length version of the [[Eigenfunction Matching for a Submerged Semi-Infinite Dock]]. The full
+
== Introduction ==
 +
 
 +
This is the extension of [[Eigenfunction Matching for a Submerged Finite Dock]] using
 +
[[:Category:Symmetry in Two Dimensions|Symmetry in Two Dimensions]].. The full
 
theory is not presented here, and details of the matching method can be found in  
 
theory is not presented here, and details of the matching method can be found in  
[[Eigenfunction Matching for a Submerged Semi-Infinite Dock]] and [[Eigenfunction Matching for a Finite Dock]]
+
[[Eigenfunction Matching for a Submerged Semi-Infinite Dock]] and [[Two Identical Docks using Symmetry]]
  
=Governing Equations=
+
==Governing Equations==
  
 
We begin with the [[Frequency Domain Problem]] for the submerged dock in
 
We begin with the [[Frequency Domain Problem]] for the submerged dock in
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<center>
 
<center>
 
<math>
 
<math>
\partial_z\phi=0, \,\, z=-d,\,-L<x>L,
+
\partial_z\phi=0, \,\, z=-d,\,-L_2<x<-L_1,\,\,{\rm and}\,\,L_1<x<L_2
 
</math>
 
</math>
 
</center>
 
</center>
Line 37: Line 40:
 
and a wave propagating away.
 
and a wave propagating away.
  
=Solution Method=
+
==Solution Method==
  
 
We use [http://en.wikipedia.org/wiki/Separation_of_Variables separation of variables] in the three regions, <math>x<0</math>
 
We use [http://en.wikipedia.org/wiki/Separation_of_Variables separation of variables] in the three regions, <math>x<0</math>
Line 48: Line 51:
 
<center>
 
<center>
 
<math>
 
<math>
\phi^{\mathrm{I}}  =e^{-k_{0}(x+L)}\phi_{0}\left(
+
\phi^{\mathrm{I}}  =e^{-k^{h}_{0}(x+L_2)}\phi_{0}\left(
 
z\right)  
 
z\right)  
 
</math>
 
</math>
 
</center>
 
</center>
  
The potential can
+
We use [[:Category:Symmetry in Two Dimensions|Symmetry in Two Dimensions]] and express the symmetric solution
be expanded as
+
as
 
<center>
 
<center>
 
<math>
 
<math>
\phi(x,z)=e^{-k_{0}^h (x+L)}\phi_{0}^h\left(
+
\phi(x,z)=e^{-k_{0}^h (x+L_2)}\phi_{0}^h\left(
z\right) + \sum_{m=0}^{\infty}a_{m}e^{k_{m}^h x}\phi_{m}^h(z), \;\;x<-L
+
z\right) + \sum_{m=0}^{\infty}a_{m}^{s}e^{k_{m}^h (x+L_2)}\phi_{m}^h(z), \;\;x<-L_2
 
</math>
 
</math>
 
</center>
 
</center>
 
<center>
 
<center>
 
<math>
 
<math>
\phi(x,z)= \sum_{m=0}^{\infty}b_{m}
+
\phi(x,z)= \sum_{m=0}^{\infty}b_{m}^{s}
e^{-k_{m}^d (x+L)}\phi_{m}^d(z)
+
e^{-k_{m}^d (x+L_2)}\phi_{m}^d(z)
+ \sum_{m=0}^{\infty}c_{m}
+
+ \sum_{m=0}^{\infty}c_{m}^{s}
e^{k_{m}^d (x-L)}\phi_{m}^d(z)
+
e^{k_{m}^d (x+L_1)}\phi_{m}^d(z)
, \;\;-d<z<0,\,\,-L<x<L
+
, \;\;-d<z<0,\,\,x<-L_2,\,-L_1<x<L_1, {\rm or} \, x>L_2
 
</math>
 
</math>
 
</center>
 
</center>
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<center>
 
<center>
 
<math>
 
<math>
\phi(x,z)= \sum_{m=0}^{\infty}d_{m}
+
\phi(x,z)= d_0^{s}\frac{x+L_1}{L_2-L_1} + \sum_{m=1}^{\infty}d_{m}^{s}
e^{\kappa_{m} (x+L)}\psi_{m}(z)
+
e^{\kappa_{m} (x+L_2)}\psi_{m}(z)
+\sum_{m=0}^{\infty}e_{m}
+
+
e^{-\kappa_{m} (x-L)}\psi_{m}(z)
+
e_0^{s}\frac{x+L_2}{L_2-L_1}
, \;\;-h<z<-d,\,\,-L<x>L
+
\sum_{m=0}^{\infty}e_{m}^{s}
 +
e^{-\kappa_{m} (x+L_1)}\psi_{m}(z)
 +
, \;\;-h<z<-d,\,\,\,-L_2<x<-L_1, {\rm or} \, L_1<x<L_2,
 
</math>
 
</math>
 
</center>
 
</center>
 
<center>
 
<center>
 
<math>
 
<math>
\phi(x,z)= \sum_{m=0}^{\infty}f_{m}e^{-k_{m}^h (x-L)}\phi_{m}^h(z), \;\;x>L
+
\phi(x,z)= \sum_{m=0}^{\infty}f_{m}^{s}\frac{\cosh(k_{m}^h x)}{\cosh(k_m^h L)}\phi_{m}^h(z), \;\;x>L
 
</math>
 
</math>
 
</center>
 
</center>
Line 89: Line 94:
 
as can the solution method and the method to extend the solution to waves incident at an angle.
 
as can the solution method and the method to extend the solution to waves incident at an angle.
  
= Matlab Code =
+
The anti-symmetric solution is
 +
<center>
 +
<math>
 +
\phi(x,z)=e^{-k_{0}^h (x+L_2)}\phi_{0}^h\left(
 +
z\right) + \sum_{m=0}^{\infty}a_{m}^{a}e^{k_{m}^h (x+L_2)}\phi_{m}^h(z), \;\;x<-L_2
 +
</math>
 +
</center>
 +
<center>
 +
<math>
 +
\phi(x,z)= \sum_{m=0}^{\infty}b_{m}^{a}
 +
e^{-k_{m}^d (x+L_2)}\phi_{m}^d(z)
 +
+ \sum_{m=0}^{\infty}c_{m}^{a}
 +
e^{k_{m}^d (x+L_1)}\phi_{m}^d(z)
 +
, \;\;-d<z<0,\,\,x<-L_2,\,-L_1<x<L_1, {\rm or} \, x>L_2
 +
</math>
 +
</center>
 +
and
 +
<center>
 +
<math>
 +
\phi(x,z)= d_0^{a}\frac{x+L_1}{L_2-L_1} + \sum_{m=1}^{\infty}d_{m}^{a}
 +
e^{-\kappa_{m} (x+L_2)}\psi_{m}(z)
 +
+
 +
e_0^{a}\frac{x+L_2}{L_2-L_1}
 +
\sum_{m=1}^{\infty}e_{m}^{a}
 +
e^{\kappa_{m} (x+L_1)}\psi_{m}(z)
 +
, \;\;-h<z<-d,\,\,\,-L_2<x<-L_1, {\rm or} \, L_1<x<L_2,
 +
</math>
 +
</center>
 +
<center>
 +
<math>
 +
\phi(x,z)= \sum_{m=0}^{\infty}f_{m}^{a}\frac{\sinh(k_{m}^h x)}{\sinh(k_m^h L)}\phi_{m}^h(z), \;\;x>L
 +
</math>
 +
</center>
 +
 
 +
== Matlab Code ==
  
A program to calculate the coefficients for the submerged semi-infinite dock problems can be found here
+
A program to calculate the coefficients for the submerged two finite dock problem can be found here
[http://www.math.auckland.ac.nz/~meylan/code/eigenfunction_matching/submerged_finite_dock.m submerged_finite_dock.m]
+
[http://www.math.auckland.ac.nz/~meylan/code/eigenfunction_matching/two_submerged_finite_docks_symmetry.m two_submerged_finite_docks_symmetry.m]
  
== Additional code ==
+
=== Additional code ===
  
 
This program requires
 
This program requires
[http://www.math.auckland.ac.nz/~meylan/code/dispersion/dispersion_free_surface.m dispersion_free_surface.m]
+
* {{free surface dispersion equation code}}
to run
+
 
  
 
[[Category:Eigenfunction Matching Method]]
 
[[Category:Eigenfunction Matching Method]]
 
[[Category:Pages with Matlab Code]]
 
[[Category:Pages with Matlab Code]]
 
[[Category:Complete Pages]]
 
[[Category:Complete Pages]]
 +
[[Category:Symmetry in Two Dimensions|Symmetry in Two Dimensions]]

Latest revision as of 00:00, 17 October 2009


Introduction

This is the extension of Eigenfunction Matching for a Submerged Finite Dock using Symmetry in Two Dimensions.. The full theory is not presented here, and details of the matching method can be found in Eigenfunction Matching for a Submerged Semi-Infinite Dock and Two Identical Docks using Symmetry

Governing Equations

We begin with the Frequency Domain Problem for the submerged dock in the region [math]\displaystyle{ x\gt 0 }[/math] (we assume [math]\displaystyle{ e^{i\omega t} }[/math] time dependence). The water is assumed to have constant finite depth [math]\displaystyle{ h }[/math] and the [math]\displaystyle{ z }[/math]-direction points vertically upward with the water surface at [math]\displaystyle{ z=0 }[/math] and the sea floor at [math]\displaystyle{ z=-h }[/math]. The boundary value problem can therefore be expressed as

[math]\displaystyle{ \Delta\phi=0, \,\, -h\lt z\lt 0, }[/math]

[math]\displaystyle{ \phi_{z}=0, \,\, z=-h, }[/math]

[math]\displaystyle{ \partial_z\phi=\alpha\phi, \,\, z=0, }[/math]

[math]\displaystyle{ \partial_z\phi=0, \,\, z=-d,\,-L_2\lt x\lt -L_1,\,\,{\rm and}\,\,L_1\lt x\lt L_2 }[/math]

We must also apply the Sommerfeld Radiation Condition as [math]\displaystyle{ |x|\rightarrow\infty }[/math]. This essentially implies that the only wave at infinity is propagating away and at negative infinity there is a unit incident wave and a wave propagating away.

Solution Method

We use separation of variables in the three regions, [math]\displaystyle{ x\lt 0 }[/math] [math]\displaystyle{ -d\lt z\lt 0,\,\,x\gt 0 }[/math], and [math]\displaystyle{ -h\lt z\lt -d,\,\,x\gt 0 }[/math]. The first two regions use the free-surface eigenfunction and the third uses the dock eigenfunctions. Details can be found in Eigenfunction Matching for a Semi-Infinite Dock.

The incident potential is a wave of amplitude [math]\displaystyle{ A }[/math] in displacement travelling in the positive [math]\displaystyle{ x }[/math]-direction. The incident potential can therefore be written as

[math]\displaystyle{ \phi^{\mathrm{I}} =e^{-k^{h}_{0}(x+L_2)}\phi_{0}\left( z\right) }[/math]

We use Symmetry in Two Dimensions and express the symmetric solution as

[math]\displaystyle{ \phi(x,z)=e^{-k_{0}^h (x+L_2)}\phi_{0}^h\left( z\right) + \sum_{m=0}^{\infty}a_{m}^{s}e^{k_{m}^h (x+L_2)}\phi_{m}^h(z), \;\;x\lt -L_2 }[/math]

[math]\displaystyle{ \phi(x,z)= \sum_{m=0}^{\infty}b_{m}^{s} e^{-k_{m}^d (x+L_2)}\phi_{m}^d(z) + \sum_{m=0}^{\infty}c_{m}^{s} e^{k_{m}^d (x+L_1)}\phi_{m}^d(z) , \;\;-d\lt z\lt 0,\,\,x\lt -L_2,\,-L_1\lt x\lt L_1, {\rm or} \, x\gt L_2 }[/math]

and

[math]\displaystyle{ \phi(x,z)= d_0^{s}\frac{x+L_1}{L_2-L_1} + \sum_{m=1}^{\infty}d_{m}^{s} e^{\kappa_{m} (x+L_2)}\psi_{m}(z) + e_0^{s}\frac{x+L_2}{L_2-L_1} \sum_{m=0}^{\infty}e_{m}^{s} e^{-\kappa_{m} (x+L_1)}\psi_{m}(z) , \;\;-h\lt z\lt -d,\,\,\,-L_2\lt x\lt -L_1, {\rm or} \, L_1\lt x\lt L_2, }[/math]

[math]\displaystyle{ \phi(x,z)= \sum_{m=0}^{\infty}f_{m}^{s}\frac{\cosh(k_{m}^h x)}{\cosh(k_m^h L)}\phi_{m}^h(z), \;\;x\gt L }[/math]

The definition of all terms can be found in Eigenfunction Matching for Submerged Semi-Infinite Dock, as can the solution method and the method to extend the solution to waves incident at an angle.

The anti-symmetric solution is

[math]\displaystyle{ \phi(x,z)=e^{-k_{0}^h (x+L_2)}\phi_{0}^h\left( z\right) + \sum_{m=0}^{\infty}a_{m}^{a}e^{k_{m}^h (x+L_2)}\phi_{m}^h(z), \;\;x\lt -L_2 }[/math]

[math]\displaystyle{ \phi(x,z)= \sum_{m=0}^{\infty}b_{m}^{a} e^{-k_{m}^d (x+L_2)}\phi_{m}^d(z) + \sum_{m=0}^{\infty}c_{m}^{a} e^{k_{m}^d (x+L_1)}\phi_{m}^d(z) , \;\;-d\lt z\lt 0,\,\,x\lt -L_2,\,-L_1\lt x\lt L_1, {\rm or} \, x\gt L_2 }[/math]

and

[math]\displaystyle{ \phi(x,z)= d_0^{a}\frac{x+L_1}{L_2-L_1} + \sum_{m=1}^{\infty}d_{m}^{a} e^{-\kappa_{m} (x+L_2)}\psi_{m}(z) + e_0^{a}\frac{x+L_2}{L_2-L_1} \sum_{m=1}^{\infty}e_{m}^{a} e^{\kappa_{m} (x+L_1)}\psi_{m}(z) , \;\;-h\lt z\lt -d,\,\,\,-L_2\lt x\lt -L_1, {\rm or} \, L_1\lt x\lt L_2, }[/math]

[math]\displaystyle{ \phi(x,z)= \sum_{m=0}^{\infty}f_{m}^{a}\frac{\sinh(k_{m}^h x)}{\sinh(k_m^h L)}\phi_{m}^h(z), \;\;x\gt L }[/math]

Matlab Code

A program to calculate the coefficients for the submerged two finite dock problem can be found here two_submerged_finite_docks_symmetry.m

Additional code

This program requires