Strouhal number formula |
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\( Sr \;=\; \dfrac{ f \cdot l_c }{v }\) (Strouhal Number) \( f \;=\; \dfrac{ Sr \cdot v}{l_c }\) \( l_c \;=\; \dfrac{ Sr \cdot v}{f }\) \( v \;=\; \dfrac{ f \cdot l_c}{Sr }\) |
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| Symbol | English | Metric |
| \( St \) = Strouhal Number | \(dimensionless\) | \(dimensionless\) |
| \( f \) = Frequency of Vortex Shedding | \(dimensionless\) | \(dimensionless\) |
| \( l_c \) = Characteristic Length | \(ft\) | \(m\) |
| \( v \) = Flow Velocity | \(ft\;/\;sec\) | \(m\;/\;s\) |
Strouhal number, abbreviated as St, a dimensionless number, is used in fluid dynamics to describe the relationship between the frequency of vortex shedding behind a bluff body and the flow velocity. It is the ratio of inertial forces due to the unsteadiness of the flow or acceleration of inertial forces due to the changes in velocity between points in a flow field.
The Strouhal number provides information about the oscillating nature of the flow. It is commonly used in the study of fluid dynamics, aerodynamics, and hydrodynamics, particularly in relation to flow induced vibrations and vortex shedding behind structures such as cylinders, airfoils, or chimneys. The Strouhal number can help engineers and scientists understand and predict the behavior of fluid flow around these structures.
Strouhal Number Interpretation
- High St - Indicates a high oscillation frequency relative to the flow speed. This might mean rapid vortex shedding or fluttering in a system.
- Low St - Suggests slower oscillations relative to the flow, implying a more stable or less dynamic wake structure.
