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Motivation


One of the key challenges in Pipe Flow Dynamics is to predict the pressure distribution along the pipe during the stationary fluid transport.

In many practical cases the stationary pressure distribution can be approximated by Isothermal or Quasi-isothermal homogenous fluid flow model.

Pipeline Flow Pressure Model is addressing this problem with account of the varying pipeline trajectory, gravity effects and fluid friction with pipeline walls.


Inputs & Outputs


InputsOutputs

LaTeX Math Inline
bodyT_s

Intake temperature 

LaTeX Math Inline
bodyp(l)

Pressure distribution along the pipe

LaTeX Math Inline
bodyp_s

Intake pressure 

LaTeX Math Inline
bodyq(l)

Flowrate distribution along the pipe

LaTeX Math Inline
bodyq_s

Intake flowrate 

LaTeX Math Inline
bodyu(l)

Flow velocity distribution along the pipe

LaTeX Math Inline
bodyz(l)

Pipeline trajectory TVDss

LaTeX Math Inline
body\theta (l)


Pipeline trajectory inclination,

LaTeX Math Inline
body--uriencoded--\displaystyle \cos \theta (l) = \frac%7Bdz%7D%7Bdl%7D



LaTeX Math Inline
body--uriencoded--%7B\bf r%7D(l)



LaTeX Math Inline
bodyT(l)

Along-pipe temperature profile 



LaTeX Math Inline
body\rho(T, p)



LaTeX Math Inline
body\mu(T, p)



LaTeX Math Inline
bodyA

Pipe cross-section area  

LaTeX Math Inline
body\epsilon

Inner pipe wall roughness



Assumptions



Equations




LaTeX Math Block
anchorPP
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\bigg( 1 -  \frac{c(p) \, \rho_s^2 \, q_s^2}{A^2}   \bigg )  \frac{dp}{dl} = \rho \, g \, \frac{dz}{dl}  - \frac{\rho_s^2 \, q_s^2 }{2 A^2 d} \frac{f({\rm Re}, \, \epsilon)}{\rho}



LaTeX Math Block
anchor1
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q(l) = \frac{\rho_s \cdot q_0}{\rho}



LaTeX Math Block
anchor1
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u(l) = \frac{\rho_s \cdot q_s}{\rho \cdot A}



LaTeX Math Block
anchorp0
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p(l=0) = p_s



LaTeX Math Block
anchorp0
alignmentleft
q(l=0) = q_s



LaTeX Math Block
anchorp0
alignmentleft
\rho(T_s, p_s) = \rho_s


where

LaTeX Math Inline
body--uriencoded--f(%7B\rm Re%7D, \, \epsilon)

Darcy friction factor

LaTeX Math Inline
body--uriencoded--\displaystyle %7B\rm Re%7D = \frac%7Bu(l) \cdot d%7D%7B\nu(l)%7D = \frac%7B4 \rho_s q_s%7D%7B\pi d%7D \frac%7B1%7D%7B\mu(T, p)%7D

Reynolds number

LaTeX Math Inline
body--uriencoded--\displaystyle d = \sqrt%7B \frac%7B4 A%7D%7B\pi%7D%7D

characteristic linear dimension of the pipe

(or exactly a pipe diameter in case of a circular pipe)


See Derivation of Stationary Isothermal Homogenous Pipe Flow Pressure Profile @model.


Approximations



Incompressible pipe flow 
LaTeX Math Inline
body\rho(T, p) = \rho_s
with constant viscosity 
LaTeX Math Inline
body\mu(T, p) = \mu_s


Pressure profilePressure gradient profileFluid velocityFluid rate


LaTeX Math Block
anchorPPconst
alignmentleft
p(l) = p_s + \rho_s \, g \, z(l) - \frac{\rho_s \, q_s^2 }{2 A^2 d} \, f_s \, l



LaTeX Math Block
anchorgradP
alignmentleft
\frac{dp}{dl} = \rho_s \, g \cos \theta(l) - \frac{\rho_s \, q_s^2 }{2 A^2 d} \, f_s



LaTeX Math Block
anchor1
alignmentleft
q(l) =q_s = \rm const



LaTeX Math Block
anchor1
alignmentleft
u(l) = u_s = \frac{q_s}{A} = \rm const


where

LaTeX Math Inline
body\theta(l)

trajectory inclination


Expand
titleDerivation


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Incompressible fluid 

LaTeX Math Inline
body\rho(T, p) = \rho_s = \rm const
 means that compressibility vanishes 
LaTeX Math Inline
bodyc(p) = 0
 and fluid velocity is going to be constant along the pipeline trajectory 
LaTeX Math Inline
body--uriencoded--u(l) = u_s = \frac%7Bq_s%7D%7BA%7D = \rm const
.

For the constant viscosity 

LaTeX Math Inline
body\mu(T, p) = \mu_s = \rm const
 along the pipeline trajectory the Reynolds number 
LaTeX Math Inline
body--uriencoded--\displaystyle %7B\rm Re%7D = \frac%7B4 \rho_s q_s%7D%7B\pi d%7D \frac%7B1%7D%7B\mu_s%7D = \rm const
 and Darcy friction factor 
LaTeX Math Inline
body--uriencoded--f(%7B\rm Re%7D, \, \epsilon) = f_s = \rm const
 are going to be constant along the pipeline trajectory.

Equation 

LaTeX Math Block Reference
anchorPP
 becomes:

LaTeX Math Block
anchorPP
alignmentleft
\frac{dp}{dl} = \rho_s \, g \, \frac{dz}{dl}  - \frac{\rho_s \, q_s^2 }{2 A^2 d} f_s

which leads to 

LaTeX Math Block Reference
anchorgradP
 after substituting 
LaTeX Math Inline
body--uriencoded--\displaystyle \cos \theta(l) = \frac%7Bdz(l)%7D%7Bdl%7D
  and can be explicitly integrated leading to 
LaTeX Math Block Reference
anchorPPconst
.



The first term in the right side of 

LaTeX Math Block Reference
anchorgradP
defines the hydrostatic column of static fluid while the last term defines the friction losses under fluid movement:


In most practical applications in water producing or water injecting wells, water can be considered as incompressible and friction factor  can be assumed constant

LaTeX Math Inline
body f(l) = f_s = \rm const
 along-hole ( see  Darcy friction factor in water producing/injecting wells ).



References


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