Reynolds number for gas, abbreviated as \( Re_g \), a dimensionless number used in fluid dynamics, including when dealing with gases. It essentially expresses the ratio of inertial forces to viscous forces within a fluid. When applied to gases, this number helps predict the flow's behavior, determining whether it will be laminar (smooth) or turbulent (chaotic). Factors influencing the Reynolds number for a gas include the gas's density, its velocity, a characteristic length (like the diameter of a pipe), and the gas's viscosity. A low Reynolds number indicates viscous forces dominate, leading to laminar flow, while a high Reynolds number signifies inertial forces prevail, resulting in turbulent flow. This concept is vital in various applications, from designing pipelines to understanding aerodynamic forces on aircraft.
Reynolds Number for Gas Formula |
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\( Re_g \;=\; 20,100 \cdot \dfrac{ SG_g \cdot Q }{ d \cdot \eta } \) (Reynolds Number for Gas) \( SG_g \;=\; \dfrac{ Re_g \cdot d \cdot \eta }{ 20,100 \cdot Q }\) \( Q \;=\; \dfrac{ Re_g \cdot d \cdot \eta }{ 20,100 \cdot SG }\) \( d \;=\; \dfrac{ SG_g \cdot Q \cdot 20,100 }{ Re_g \cdot \eta }\) \( \eta \;=\; \dfrac{ SG_g \cdot Q \cdot 20,100 }{ Re_g \cdot d }\) |
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| Symbol | English | Metric |
| \( Re_g \) = Reynolds Number | \( dimensionless \) | \( dimensionless \) |
| \( SG_g \) = Gas Specific Gravity | \( dimensionless \) | \( dimensionless \) |
| \( Q \) = Gas Flow Rate | \(ft^3\;/\;sec\) | \(m^3\;/\;s\) |
| \( d \) = Pipe Inside Diameter | \( in\) | \( mm \) |
| \( \eta \) (Greek symbol eta) = Gas Viscosity | \(lbf - sec\;/\;ft^2\) | \(Pa-s\) |
