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titleDerivation


Panel
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Incompressible fluid 

LaTeX Math Inline
body\rho(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 = \frac%7B4 \rho_0 q_0%7D%7B\pi d%7D \frac%7B1%7D%7B\mu_0%7D = \rm const
 and Darcy friction factor 
LaTeX Math Inline
body--uriencoded--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{\rho_0 \, q_0^2 }{2 A^2 d} f_0

and can be explicitly integrated leading which leads to 

LaTeX Math Block Reference
anchorPPconstgradP
. after substituting Substituting the   
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:

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