Strouhal Number Calculator

Strouhal Number Formula:

\[ S = \frac{n \times D_{vortex}}{V_{\infty}} \]

Frequency of Vortex Shedding:

Diameter of Cylinder with Vortex:

Freestream Velocity of Fluid:

m/s

Strouhal Number:

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1. What is the Strouhal Number?

The Strouhal Number is a dimensionless number that describes oscillating flow mechanisms, particularly in fluid dynamics. It relates the frequency of vortex shedding to the velocity and characteristic length of an object in a fluid flow.

2. How Does the Calculator Work?

The calculator uses the Strouhal Number formula:

\[ S = \frac{n \times D_{vortex}}{V_{\infty}} \]

Where:

\( S \) — Strouhal Number (dimensionless)
\( n \) — Frequency of Vortex Shedding (Hz)
\( D_{vortex} \) — Diameter of Cylinder with Vortex (m)
\( V_{\infty} \) — Freestream Velocity of Fluid (m/s)

Explanation: The Strouhal Number characterizes the oscillating flow patterns behind bluff bodies and is particularly important in the study of vortex-induced vibrations.

3. Importance of Strouhal Number

Details: The Strouhal Number is crucial for understanding and predicting flow-induced vibrations, aerodynamic noise generation, and the behavior of structures in fluid flows such as bridges, buildings, and offshore structures.

4. Using the Calculator

Tips: Enter the frequency of vortex shedding in Hz, the diameter of the cylinder in meters, and the freestream velocity in m/s. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range of Strouhal Numbers?
A: For circular cylinders in cross-flow, the Strouhal Number typically ranges from 0.18 to 0.22, though it can vary with Reynolds number and surface roughness.

Q2: How does Reynolds number affect the Strouhal Number?
A: The Strouhal Number generally remains relatively constant over a wide range of Reynolds numbers for many bluff body shapes, particularly in the subcritical flow regime.

Q3: What practical applications use the Strouhal Number?
A: Applications include predicting vortex-induced vibrations in offshore structures, designing heat exchangers, analyzing flow around buildings, and studying fish swimming mechanics.

Q4: Can the Strouhal Number be used for non-cylindrical shapes?
A: Yes, the Strouhal Number concept applies to various bluff body shapes, though the characteristic length and specific values may differ from circular cylinders.

Q5: How is vortex shedding frequency measured experimentally?
A: Vortex shedding frequency can be measured using various techniques including hot-wire anemometry, pressure transducers, flow visualization, or laser Doppler velocimetry.