Joukowsky equation, also called Joukowsky shock, and watter hammer, is a method of determining the surge pressures that will be experienced in the piping system. The flow velocity of the water itself (before the sudden change) is different from the wave speed. Water hammer occurs when this flow velocity changes abruptly, and the resulting pressure surge is proportional to the change in velocity.
oukowsky Equation Formula |
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\( \Delta p \;=\; \rho \cdot a \cdot \Delta v \) (Joukowsky Equation) \( \rho \;=\; \dfrac{ \Delta p }{ a \cdot \Delta v }\) \( a \;=\; \dfrac{ \Delta p }{ \rho \cdot \Delta v }\) \( \Delta v \;=\; \dfrac{ \Delta p }{ \rho \cdot a }\) |
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| Symbol | English | Metric |
| \( \Delta p \) = Pressure Surge | \(lbf \;/\; ft^2\) | \(Pa\) |
| \( \rho \) (Greek symbol rho) = Fluid Density | \(lbm \;/\; ft^3\) | \(kg \;/\; m^3\) |
| \( a \) = Wave Speed | \(in^3\) | \(mm^3\) |
| \( \Delta v \) = Velocity Change | \(dimensionless\) | \(dimensionless\) |
