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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 steady-state 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

Fluid temperature at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
bodyT(l)

Along-pipe temperature profile 

LaTeX Math Inline
bodyp_0

Fluid pressure at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
body\rho(T, p)

Fluid density 

LaTeX Math Inline
bodyq_0

Fluid flowrate  at inlet point (

LaTeX Math Inline
bodyl=0
)

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


Stationary flowHomogenous flowIsothermal or Quasi-isothermal conditions

Constant cross-section pipe area

LaTeX Math Inline
bodyA
along hole


Equations



LaTeX Math Block
anchorPP
alignmentleft
\left(\rho(p) -  j_m^2 \cdot c(p)   \right)  \frac{dp}{dl} = \rho^2(p) \, g \, \cos \theta(l)  - \frac{ j_m^2 }{2 d} \cdot  f({\rm Re}, \, \epsilon)



LaTeX Math Block
anchorp0
alignmentleft
p(l=0) = p_0




LaTeX Math Block
anchor1
alignmentleft
u(l) = \frac{\rho_0 \cdot q_0}{\rho(T(l), p(l))) \cdot A}



LaTeX Math Block
anchor1
alignmentleft
q(l) = \frac{\rho_0 \cdot q_0}{\rho(T(l),p(l))}


where

LaTeX Math Inline
body--uriencoded--\displaystyle j_m =\frac%7B \rho_0 \, q_0%7D%7BA%7D

mass flux

LaTeX Math Inline
bodyq_0 = q(l=0)

Fluid flowrate at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
body\rho_0 = \rho(T_0, p_0)

Fluid density at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
bodyс(p)

Fluid Compressibility

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%7Bj_m \cdot d%7D%7B\mu(T, p)%7D

Reynolds number in Pipe Flow

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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See Derivation of Pressure Profile in Steady-State Homogeneous Pipe Flow @model.



Approximations



Incompressible pipe flow 

LaTeX Math Inline
body\rho(T, p) = \rho_0
with constant viscosity 
LaTeX Math Inline
body\mu(T, p) = \mu_0

Pressure Profile in Incompressible Isoviscous Stationary Quasi-Isothermal Pipe Flow @model

Pressure profilePressure gradient profileFluid velocityFluid rate


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



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



LaTeX Math Block
anchor1
alignmentleft
q(l) =q_0 = \rm const



LaTeX Math Block
anchor1
alignmentleft
u(l) = u_0 = \frac{q_0}{A} = \rm const


where

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

Darcy friction factor at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
body--uriencoded--\displaystyle %7B\rm Re%7D_0= \frac%7Bj_m \, d%7D%7B\mu_0%7D

Reynolds number at inlet point (

LaTeX Math Inline
bodyl=0
)

LaTeX Math Inline
body\mu_0 = \mu(T_0, p_0)

Dynamic Fluid Viscosity at inlet point (

LaTeX Math Inline
bodyl=0
)


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 many practical applications the water in 
water producing wells or water injecting wells 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


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