Strouhal Number

Overview

Engineering reference data for Strouhal Number in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Interpretation

The Strouhal Number ($St$) is a dimensionless parameter used to characterize oscillating unsteady fluid flow. It represents the ratio of the inertial forces due to the flow's unsteadiness (local acceleration) to the inertial forces caused by convective acceleration (changes in velocity along the flow field).

A key application is in analyzing the shedding of vortices behind bluff bodies, such as a stone in a river or an obstruction in a vortex flow meter.

Applications

The concept is vital in several engineering contexts:

• Vortex Shedding Frequency: The dimensionless frequency of vortex shedding ($f$) from a body is often characterized by the Strouhal Number. The relationship is given by: $St = \frac{f \cdot D}{U}$ where $D$ is the characteristic length (e.g., cylinder diameter) and $U$ is the free-stream flow velocity.

• Aeroacoustics & Flow-Induced Vibration: The Strouhal Number is critical for predicting the frequency of flow-induced vibrations and the resulting sound in structures like chimneys, cables, or heat exchanger tubes.

References

• Original Source