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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.


Outputs


LaTeX Math Inline
bodyp(l)

Pressure distribution along the pipe

LaTeX Math Inline
bodyq(l)

Flowrate distribution along the pipe

LaTeX Math Inline
bodyu(l)

Flow velocity distribution along the pipe

Inputs


LaTeX Math Inline
bodyT_0

Intake temperature 

LaTeX Math Inline
bodyT(l)

Along-pipe temperature profile 

LaTeX Math Inline
bodyp_0

Intake pressure 

LaTeX Math Inline
body\rho(T, p)


LaTeX Math Inline
bodyq_0

Intake flowrate 

LaTeX Math Inline
body\mu(T, p)


LaTeX Math Inline
bodyz(l)

Pipeline trajectory TVDss

LaTeX Math Inline
bodyA

Pipe cross-section area  
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\epsilon

Inner pipe wall roughness

Assumptions


Steady-State flowIsothermal or Quasi-isothermal flow

LaTeX Math Inline
body--uriencoded--\displaystyle \frac%7B\partial p%7D%7B\partial t%7D = 0 \rightarrow p(t,l) = p(l)

LaTeX Math Inline
body--uriencoded--\displaystyle \frac%7B\partial T%7D%7B\partial t%7D =0 \rightarrow T(t,l) = T(l)

Homogenous flow

Constant cross-section pipe area

LaTeX Math Inline
bodyA
along hole

LaTeX Math Inline
body--uriencoded--\displaystyle \frac%7B\partial p%7D%7B\partial \tau_x%7D =\frac%7B\partial p%7D%7B\partial \tau_y%7D =0 \rightarrow p(\tau_x,\tau_y,l) = p(l)

LaTeX Math Inline
bodyA(l) = A = \rm const

Incompressible fluid 

LaTeX Math Inline
body\rho(T, p)=\rho_0 = \rm const
 → 
LaTeX Math Inline
body\mu(T, \rho) =\mu_0 = \rm const


Equations


Pressure profilePressure gradient profile


LaTeX Math Block
anchorPPconst
alignmentleft
p(l) = p_0 + \rho_0 \, g \, \Delta z(l) - \frac{\rho_0 \, q_0^2 }{2 A^2 d} \, f_0 \, l



LaTeX Math Block
anchorgradP
alignmentleft
\frac{dp}{dl} = \rho_0 \, g \cos \theta(l) - \frac{\rho_0 \, q_0^2 }{2 A^2 d} \, f_0


Mass FluxMass Flowrate


LaTeX Math Block
anchorMassFlux
alignmentleft
j_m = \rho_0 \cdot \sqrt{\frac{2 \, d}{f_0 \, l }} \cdot \sqrt{g \, \Delta z(l) + (p_0 - p)/ \rho_0}



LaTeX Math Block
anchorMassFlowrate
alignmentleft
\dot m = j_m \cdot A = \rho_0 \cdot A \cdot \sqrt{\frac{2 \, d}{f_0 \, l }} \cdot \sqrt{g \, \Delta z(l) + (p_0 - p)/ \rho_s}


 Volumetric Flowrate

Intake Fluid velocity


LaTeX Math Block
anchorPPconst
alignmentleft
q_0 = \dot m / \rho_0 = A \cdot \sqrt{\frac{2 \, d }{ f_0 \, l }} \cdot \sqrt{  g \, \Delta z(l) + (p_0 - p)/ \rho_s }



LaTeX Math Block
anchorPPconst
alignmentleft
u_0 = j_m/ \rho_0 =q_0 / A = \sqrt{\frac{2 \, d }{ f_0 \, l }} \cdot \sqrt{  g \, \Delta z(l) + (p_0 - p)/ \rho_s }


where

LaTeX Math Inline
bodyj_m

Intake mass flux

LaTeX Math Inline
body\dot m

mass flowrate

LaTeX Math Inline
bodyu_0 = u(l=0)

Intake Fluid velocity

LaTeX Math Inline
body\Delta z(l) = z(l)-z(0)

elevation drop along pipe trajectory

LaTeX Math Inline
body--uriencoded--f_0 = f(%7B\rm Re%7D_0, \, \epsilon)

Darcy friction factor at intake point

LaTeX Math Inline
body--uriencoded--\displaystyle %7B\rm Re%7D_0 = \frac%7Bu(l) \cdot d%7D%7B\nu(l)%7D = \frac%7B4 \rho_0 q_0%7D%7B\pi d%7D \frac%7B1%7D%7B\mu_0%7D

Reynolds number at intake point

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)



Expand
titleDerivation


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Incompressible fluid 

LaTeX Math Inline
body\rho(T, p) = \rho_0 = \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_0 = \frac%7Bq_0%7D%7BA%7D = \rm const
.

For the constant viscosity 

LaTeX Math Inline
body\mu(T, p) = \mu_0 = \rm const
 along the pipeline trajectory the Reynolds number 
LaTeX Math Inline
body--uriencoded--\displaystyle %7B\rm Re%7D(l) = \frac%7Bj_m%5e2 \, d%7D%7B\mu_0%7D = \rm const
 and Darcy friction factor 
LaTeX Math Inline
body--uriencoded--f(l) = f(%7B\rm Re%7D, \, \epsilon) = f_0 = \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_0 \, g \, \frac{dz}{dl}  - \frac{j_m^2  f_0}{2 \, \rho_0 \, d}

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_0 = \rm const
 along-hole ( see  Darcy friction factor in water producing/injecting wells ).


See also

References


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