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Categorization is loosely based upon scheme used by Bruggeman (1999)
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= analytic and analytic element solutions (Strack,1989 classification) =
  
= Steady-state Confined/Unconfined Potential Flow =
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== horizontal confined flow ==
  
Governing Equation (1D or 2D):
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=== one-dimensional flow ===
  
<math>\nabla \cdot \left(k\phi \nabla h\right)=-N </math>
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=== radial flow ===
  
Where <math>\phi</math> is the saturated thickness of the aquifer [<math>L</math>], <math>N</math> is the vertical influx to the aquifer (recharge/leakage) [<math>LT^{-1}</math>], and <math>h</math> [<math>L</math>] is the head  measured with the respect to a flat aquifer base.
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=== two-dimensional flow ===
  
A common transformation (the Girinskii potential) can be used to simplified the governing equation, and make it equally valid for both confined flow (<math>\phi=H</math>) and unconfined flow (<math>\phi=h</math>):
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== shallow unconfined flow ==
  
<math>
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=== one-dimensional flow ===
\Phi=\frac{1}{2}k h^2
 
</math>
 
  
if <math>h<H</math>, and
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=== two-dimensional flow ===
  
<math>
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== combined shallow confined and unconfined flow ==
\Phi=kHh-\frac{1}{2}kH^2
 
</math>
 
  
if <math>h>H</math>. This results in the Laplace/Poisson equation:
 
  
<math>\nabla ^2\Phi=-N </math>
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=== one-dimensional flow ===
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=== radial flow ===
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== shallow unconfined flow with rainfall ==
  
The integrated discharge vector may be obtained from the gradient of the potential.
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== shallow interface flow ==
  
== One-dimensional horizontal flow ==
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== aquifers with vertically varying hydraulic conductivity ==
  
Governing Equation:
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== shallow flow in aquifers with clay laminae ==
  
<math>\frac{\partial^2 \Phi}{\partial x^2}=-N</math>
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== shallow interface flow in aquifers with impermeable laminae ==
  
'''Solution #1: Steady-state / Two Dirichlet Boundaries'''
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== shallow semiconfined flow ==
 
Boundary conditions:
 
 
<math>\Phi(0)=\Phi_1; \frac{}{} \Phi(L)=\Phi_2</math>
 
 
Solution:
 
 
<math>\Phi(x)=-\frac{1}{2}Nx^2+\left(\frac{\Phi_2-\Phi_1}{L}+\frac{1}{2}NL\right)x+\Phi_1</math>
 
  
'''Solution #2: Steady-state / One Dirichlet, One Neumann Boundary'''
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== shallow flow in systems of aquifers separated by leaky layers ==
 
Boundary conditions:
 
 
<math>\Phi(0)=\Phi_1; \frac{}{} Q_x(L)=\beta</math>
 
 
Solution:
 
 
<math>\Phi(x)=-\frac{1}{2}Nx^2+\left(-\beta+NL\right)x+\Phi_1</math>
 
  
== Two-dimensional radially-symmetric horizontal flow ==
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== transient shallow flow ==
  
Governing Equation:
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== two-dimensional flow in the vertical plane ==
  
<math>\frac{\partial}{\partial r}\left(r\frac{\partial \Phi}{\partial r}\right)=-N</math>
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== three-dimensional flow ==
  
'''Solution #1 (Steady State Thiem Solution):'''
 
  
Boundary conditions:
 
 
<math>\underset{r\rightarrow 0}{\lim}\int_0^{2\pi} rkh\frac{\partial h}{\partial r}d\theta=\underset{r\rightarrow 0}{\lim}\int_0^{2\pi} rQ_rd\theta=Q</math>
 
(i.e., the total flow out at r=0 is equal to the total flow from the well, <math>Q</math>)
 
 
<math>\Phi(R)=\Phi_0\frac{}{}</math>
 
 
Solution:
 
 
<math>\Phi(r)=-\frac{Q}{2\pi}\ln\left(\frac{r}{R}\right)+\Phi_0</math>
 
  
== Two-dimensional general horizontal flow ==
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= analytical solutions (Bruggeman,1999 classification) =
  
Governing Equation:
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== Phreatic groundwater ==
  
<math>\frac{\partial^2 \Phi}{\partial x^2}+\frac{\partial^2 \Phi}{\partial y^2}=-N</math>
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Governing Equation (1D or 2D): <math>\nabla \cdot \left(kh \nabla h\right)=S_y\frac{\partial h}{\partial t}-N </math>
  
= Transient Phreatic (Unconfined) groundwater =
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Where <math>S_y</math> is the specific yield [-], <math>N</math> is the vertical influx to the aquifer (recharge/leakage) [<math>LT^{-1}</math>], and <math>h</math> [<math>L</math>] is both the head and the saturated thickness (i.e., the head is measured with the respect to a flat aquifer base).
  
Governing Equation (1D or 2D):  
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A common transformation to linearize the steady state form of the equation is to solve the problem in terms of the Girinskii Potential:
  
<math>\nabla \cdot \left(kh \nabla h\right)=S_y\frac{\partial h}{\partial t}-N </math>
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<math>\Phi=\frac{1}{2}k h^2</math>
  
Where <math>S_y</math> is the specific yield [-], <math>N</math> is the vertical influx to the aquifer (recharge/leakage) [<math>LT^{-1}</math>], and <math>h</math> [<math>L</math>] is both the head and the saturated thickness (i.e., the head is measured with the respect to a flat aquifer base).
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Leaving us with a revised governing equation (the Poisson equation):
  
== Exact solutions ==
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<math>\nabla ^2\Phi=-N </math>
  
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=== Exact solutions ===
  
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=== One-dimensional horizontal flow ===
  
== General two-dimensional horizontal flow ==
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=== Two-dimensional radial-symmetric horizontal flow ===
  
= Transient Confined groundwater =
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=== General two-dimensional horizontal flow ===
  
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== Confined groundwater ==
  
Governing Equation (1D or 2D):
 
  
<math>\nabla \cdot \left(kH \nabla h\right)=S_sH\frac{\partial h}{\partial t}-N </math>
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Governing Equation (1D or 2D): <math>\nabla \cdot \left(kH \nabla h\right)=S_s\frac{\partial h}{\partial t}-N </math>
  
 
Where <math>S_s</math> is the specific storage [-], <math>N</math> is the vertical influx to the aquifer (recharge/leakage) [<math>LT^{-1}</math>], <math>H</math> is the saturated thickness of the aquifer and <math>h</math> [<math>L</math>] is the head, measured with respect to an arbitrary datum.
 
Where <math>S_s</math> is the specific storage [-], <math>N</math> is the vertical influx to the aquifer (recharge/leakage) [<math>LT^{-1}</math>], <math>H</math> is the saturated thickness of the aquifer and <math>h</math> [<math>L</math>] is the head, measured with respect to an arbitrary datum.
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Where <math>\alpha=\frac{k}{S_s}</math> is the hydraulic diffusivity [<math>LT^{-1}</math>]of the aquifer.  
 
Where <math>\alpha=\frac{k}{S_s}</math> is the hydraulic diffusivity [<math>LT^{-1}</math>]of the aquifer.  
  
== One-dimensional flow  ==
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=== One-dimensional flow  ===
 
 
== Two-dimensional flow ==
 
 
 
== Two-dimensional radially-symmetric flow ==
 
  
'''Solution #1 (Transient Theis Solution):'''
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=== Two-dimensional radial-symmetric flow ===
  
Boundary/initial conditions:
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=== General two-dimensional flow ===  
 
<math>\Phi(r,0)=\Phi_0\frac{}{}</math>
 
 
<math>\underset{r\rightarrow 0}{\lim}\int_0^{2\pi} rkH\frac{\partial h}{\partial r}d\theta=\underset{r\rightarrow 0}{\lim}\int_0^{2\pi} rQ_rd\theta=QH(t)</math>
 
(i.e., the total flow out at r=0 is equal to the total flow from the well, <math>Q</math>).
 
Here, <math>H(t)</math> is the heaviside function, equal to 1 for <math>t>0</math>, zero otherwise.
 
 
 
<math>\underset{r\rightarrow \infty}{\lim}\Phi(r)=\Phi_0\frac{}{}</math>
 
 
Solution:
 
 
<math>\Phi(r,t) = \Phi_0-\frac{Q}{4\pi}E_1\left(\frac{r^2 S_s}{4kt}\right)</math>
 
 
Where <math>E_1()</math> is the exponential integral (a.k.a. the "well function")
 
  
== Three-dimensional flow ==
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=== Three-dimensional spherical flow ===
  
== Three-dimensional spherically-symmetric flow ==
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=== Three-dimensional axial-symmetric flow ===
  
== Three-dimensional axially-symmetric flow ==
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=== General three-dimensional flow ===
  
= Multi-layer systems =
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== Multi-layer systems ==
  
= Dispersion =
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== Dispersion ==
  
=  Density flow (interface)=
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==  Density flow (interface)==

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