What is the St (Strouhal Number)?
The Strouhal number relates vortex shedding frequency to flow speed and body size. It predicts the rhythm of wakes behind bluff bodies and the risk of resonant vibration.
// conversions › 4 · Dimensionless Number Engines
Strouhal Number Calculator
Compute the Strouhal number from vortex shedding frequency, characteristic length and flow velocity for oscillating-flow and wake analysis.
St = f·L ÷ v
Frequently asked questions
Can you show a worked example?
f=20, L=0.1, v=10 → St = (20·0.1)/10 = 0.20 → typical von Kármán wake range.
How do I read the graph?
The visualisation places your computed St against colour-coded regime zones, with a live marker so you can see at a glance which flow or transfer regime your inputs fall into and how close you are to the next threshold.
Where is this used in real life?
Predicting vortex-induced vibration on chimneys, cables, bridges and heat-exchanger tubes.
What are the limits or edge cases?
All inputs must be physically valid; a zero in the denominator (e.g. zero viscosity, velocity or conductivity) is rejected rather than producing infinity. Regime thresholds are standard textbook values and can shift with geometry and conditions.