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LaTeX Math Inline
bodyc_t = с_\phi+ c

We start with 

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pageSingle-phase pressure diffusion @model
:

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\phi \cdot c_t \cdot \partial_t p + \nabla  {\bf u}  
+ c \cdot ( {\bf u} \, \nabla p)
= \sum_k q_k(t) \cdot \delta({\bf r}-{\bf r}_k)

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{\bf u} = - M \cdot ( \nabla p - \rho \, {\bf g})



and neglect the non-linear term 

LaTeX Math Inline
body--uriencoded--c \cdot ( %7B\bf u%7D \, \nabla p)
 for low compressibility fluid
LaTeX Math Inline
bodyc \sim 0
 or equivalently to a constant fluid density:
LaTeX Math Inline
body\rho(p) = \rho = \rm const
.

Together with constant pore compressibility 

LaTeX Math Inline
bodyc_r = \rm const
this will lead to constant total compressibility 
LaTeX Math Inline
bodyc_t = c_r + c \approx \rm const
.

Assuming that permeability and fluid viscosity do not depend on pressure

LaTeX Math Inline
bodyk(p) = k = \rm const
 and
LaTeX Math Inline
body\mu(p) = \mu = \rm const
 one arrives to the differential equation with constant coefficients

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LaTeX Math Block
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\phi \, c_t \cdot \partial_t p + \nabla  {\bf u}  
= \sum_k q_k(t) \cdot \delta({\bf r}-{\bf r}_k)

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{\bf u} = - \frac{k}{\mu} \cdot ( \nabla p - \rho \, {\bf g})

See also

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Physics / Mechanics / Continuum mechanics / Fluid Mechanics / Fluid Dynamics / Pressure Diffusion / Pressure Diffusion @model / Single-phase pressure diffusion @model

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