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LaTeX Math Block
anchorRe
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{\rm Re} = \frac{ \sum_\alpha \rho_\alpha \, u_\alpha^2 \, A_\alpha}
{\sum_\alpha \mu_\alpha \, u_\alpha \, \sqrt{A_\alpha} } =
\frac{ \sum_\alpha \rho_\alpha \, q_\alpha^2 / A_\alpha}
{\sum_\alpha \mu_\alpha \, q_\alpha / \sqrt{A_\alpha} } =
\frac{1}{\sqrt{A}} \cdot \frac{ \sum_\alpha \rho_\alpha \, q_\alpha^2 / s_\alpha}
{\sum_\alpha \mu_\alpha \, q_\alpha / \sqrt{s_\alpha} }

where

LaTeX Math Inline
body\rho_

L liquid density

\alpha

LaTeX Math Inline
body\

rho_ggas

alpha
-phase fluid density

LaTeX Math Inline
body

uliquid velocity

s_

L

\alpha

volume share occupied by 

LaTeX Math Inline
body

u_ggas velocity

\alpha
-phase 

LaTeX Math Inline
body

A_L cross-sectional area occupied by liquid 

\mu_\alpha

LaTeX Math Inline
body\alpha
-phase fluid viscosity

LaTeX Math Inline
bodyA_

g

\alpha

cross-sectional area occupied

by gas 

by 

LaTeX Math Inline
body\

mu_L liquid viscosity

alpha
-phase 

LaTeX Math Inline
bodyu_\alpha

LaTeX Math Inline
body\alpha
-phase fluid velocity

LaTeX Math Inline
body

\mu_g gas viscosity

A

total cross-sectional area


Expand
titleDerivation


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

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

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Homogeneous Pipe Flow


Homogeneous Pipe Flow is characterized by the same phase velocities: 

LaTeX Math Inline
bodyu_\alpha = u_t, \, \forall \alpha \in \Gamma
 (no slippage) and the multiphase Reynolds number takes simpler form:

LaTeX Math Block
anchor1
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{\rm Re} =\frac{ \sum_\alpha \rho_\alpha \, u_\alpha \, A_\alpha}
{\sum_\alpha \mu_\alpha \, \sqrt{A_\alpha} } =\frac{ \dot m}
{\sum_\alpha \mu_\alpha \, \sqrt{A_\alpha} } = \frac{\dot m}{\sqrt{A}} \cdot \frac{1}{ \sum_\alpha \mu_\alpha \, \sqrt{s_\alpha} }

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