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.
Assumptions
Equations
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| \bigg( 1 - \frac{c(p) \, \rho_0^2 \, q_0^2}{A^2} \bigg ) \frac{dp}{dl} = \rho(p) \, g \, \frac{dz}{dl} - \frac{\rho_0^2 \, q_0^2 }{2 A^2 d} \frac{f({\rm Re}, \, \epsilon)}{\rho(p)} |
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| u(l) = \frac{\rho_0 \cdot q_0}{\rho(p) \cdot A} |
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| q(l) = \frac{\rho_0 \cdot q_0}{\rho(p)} |
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where
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body | --uriencoded--f(%7B\rm Re%7D, \, \epsilon) |
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| Darcy friction factor |
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body | --uriencoded--\displaystyle %7B\rm Re%7D = \frac%7Bu(l) \cdot d%7D%7B\nu(l)%7D |
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| Reynolds number |
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body | --uriencoded--\displaystyle d = \sqrt%7B \frac%7B4 A%7D%7B\pi%7D%7D |
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| 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
with constant friction
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body | --uriencoded--f(%7B\rm Re%7D, \, \epsilon) = f_0 |
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Pressure profile | Pressure gradient profile | Fluid velocity | Fluid rate |
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| p(l) = p_0 + \rho \, g \, z(l) - \frac{\rho_0 \, q_0^2 }{2 A^2 d} \, f_0 \, l |
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| \frac{dp}{dl} = \rho \, g \cos \theta(l) - \frac{\rho_0 \, q_0^2 }{2 A^2 d} \, f_0 |
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| u(l) = u_0 = \frac{q_0}{A} = \rm const |
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| q(l) =q_0 = \rm const |
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where
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body | \displaystyle \cos \theta(l) = \frac{dz(l)}{dl} |
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| correction factor for trajectory inclination |
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| Incompressible fluid LaTeX Math Inline |
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body | \rho(p) = \rho_0 = \rm const |
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| means that fluid velocity is going to be constant along the trajectory LaTeX Math Inline |
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body | --uriencoded--u(l) = u_0 = \frac%7Bq_0%7D%7BA%7D = \rm const |
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| .The Reynolds number LaTeX Math Inline |
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body | --uriencoded--\displaystyle %7B\rm Re%7D = \frac%7Bu_0 \cdot d%7D%7B\nu_0%7D |
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| may still be varying along the trajectory due to the influence of temperature profile on kinematic viscosity LaTeX Math Inline |
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body | --uriencoded--\nu(l) = \frac%7B\mu(T(l))%7D%7B\rho_0%7D |
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The first term in
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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 the water can be considered as incompressible and friction factor an be assumed constant
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body | f(l) = f_s = \rm const |
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along-hole ( see
Darcy friction factor in water producing/injecting wells ).
References
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