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In multiphase flow the Darcy friction factor can be calculated as Darcy friction factor Single-phase @model with specific approximation of Reynolds number:

LaTeX Math Block
anchorRe
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{\rm Re} = \frac{ \sum_\alpha \rho_L\alpha \, u_L^2\alpha^2 \, A_L +\alpha}
{\sum_\alpha \rhomu_g\alpha \, u_g^2\alpha \, \sqrt{A_g}{\mu_L \, u_L \,\alpha} } =
\frac{ \sum_\alpha \rho_\alpha \, q_\alpha^2 / A_\alpha}
{\sum_\alpha \mu_\alpha \, q_\alpha / \sqrt{A_L} + \mu_g \, u_g\alpha} } =
\frac{1}{\sqrt{A}} \cdot \frac{ \sum_\alpha \rho_\alpha \, q_\alpha^2 / s_\alpha}
{\sum_\alpha \mu_\alpha \, q_\alpha / \sqrt{As_g\alpha} }

where

LaTeX Math Inline
body\rho_L

liquid density

LaTeX Math Inline
body\rho_g

gas density

LaTeX Math Inline
bodyu_L

liquid velocity

LaTeX Math Inline
bodyu_g

gas velocity

LaTeX Math Inline
bodyA_L

cross-sectional area occupied by liquid 

LaTeX Math Inline
bodyA_g

cross-sectional area occupied by gas 

LaTeX Math Inline
body\mu_L

liquid viscosity

LaTeX Math Inline
body\mu_g

gas viscosity

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Expand
titleDerivation


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Reynolds number represent the ration of intertial forces to viscous forces:

LaTeX Math Block
alignmentleft
{\rm Re} = \frac{\rm Intertial \ Forces}{\rm Viscocus \ Forces}




Homogeneous fluid  flow


LaTeX Math Block
anchor1
alignmentleft
{\rm Re} =\frac{ \sum_\alpha \rho_\alpha \, u_\alpha \, A_\alpha}
{\sum_\alpha \mu_\alpha \, \sqrt{A_\alpha} } =\frac{ \sum_\alpha m_\alpha}
{\sum_\alpha \mu_\alpha \, \sqrt{A_\alpha}

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 }


2-phase Gas-Liquid  flow


LaTeX Math Block
alignmentleft
{\rm Re} = \frac{\rho_L \, u_L^2 \, A_L + \rho_g \, u_g^2 \, A_g}{\mu_L \, u_L \, \sqrt{A_L} + \mu_g \, u_g \, \sqrt{A_g}}

where

LaTeX Math Inline
body\rho_L

liquid density

LaTeX Math Inline
body\rho_g

gas density

LaTeX Math Inline
bodyu_L

liquid velocity

LaTeX Math Inline
bodyu_g

gas velocity

LaTeX Math Inline
bodyA_L

cross-sectional area occupied by liquid 

LaTeX Math Inline
bodyA_g

cross-sectional area occupied by gas 

LaTeX Math Inline
body\mu_L

liquid viscosity

LaTeX Math Inline
body\mu_g

gas viscosity



See also

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Physics / Fluid Dynamics / Pipe Flow Dynamics / Darcy–Weisbach equation / Darcy friction factor 

Reference

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L. E. Ortiz-Vidala, N. Mureithib, and O. M. H. Rodrigueza ,TWO-PHASE FRICTION FACTOR IN GAS-LIQUID PIPE FLOW, Engenharia Térmica (Thermal Engineering), Vol. 13, No. 2, December 2014, p. 81-88

Shannak, B. A., 2008, Frictional Pressure Drop of Gas Liquid Two-Phase Flow in Pipes, Nuclear Engineering and Design, Vol. 238, pp. 3277-3284., doi.org/10.1016/j.nucengdes.2008.08.015

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