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

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= Introduction =
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{{complete pages}}
 +
 
 +
== Introduction ==
  
 
This is the extension of [[Eigenfunction Matching for a Submerged Finite Dock]] using  
 
This is the extension of [[Eigenfunction Matching for a Submerged Finite Dock]] using  
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[[Eigenfunction Matching for a Submerged Semi-Infinite Dock]] and [[Two Identical Docks using Symmetry]]
 
[[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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and a wave propagating away.
 
and a wave propagating away.
  
=Solution Method=
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==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>
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<center>
 
<center>
 
<math>
 
<math>
\phi^{\mathrm{I}}  =e^{-k_{0}(x+L_2)}\phi_{0}\left(
+
\phi^{\mathrm{I}}  =e^{-k^{h}_{0}(x+L_2)}\phi_{0}\left(
 
z\right)  
 
z\right)  
 
</math>
 
</math>
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<math>
 
<math>
 
\phi(x,z)= d_0^{a}\frac{x+L_1}{L_2-L_1} + \sum_{m=1}^{\infty}d_{m}^{a}
 
\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^{-\kappa_{m} (x+L_2)}\psi_{m}(z)
 
+
 
+
 
e_0^{a}\frac{x+L_2}{L_2-L_1}  
 
e_0^{a}\frac{x+L_2}{L_2-L_1}  
\sum_{m=0}^{\infty}e_{m}^{a}
+
\sum_{m=1}^{\infty}e_{m}^{a}
e^{-\kappa_{m} (x+L_1)}\psi_{m}(z)
+
e^{\kappa_{m} (x+L_1)}\psi_{m}(z)
 
, \;\;-h<z<-d,\,\,\,-L_2<x<-L_1, {\rm or} \, L_1<x<L_2,
 
, \;\;-h<z<-d,\,\,\,-L_2<x<-L_1, {\rm or} \, L_1<x<L_2,
 
</math>
 
</math>
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</center>
 
</center>
  
= Matlab Code =
+
== Matlab Code ==
  
 
A program to calculate the coefficients for the submerged two finite dock problem 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/two_submerged_finite_docks_symmetry.m two_submerged_finite_docks_symmetry.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 ==
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=== Additional code ===
  
 
This program requires
 
This program requires

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