Bond Number

Bond Number Calculator

Bond Number Calculator

The Bond number (Bo) is a dimensionless parameter used in fluid mechanics to characterize the relative importance of gravitational forces to surface tension forces in a fluid system. It’s named after the Hungarian physicist Loránd Eötvös, who made significant contributions to the study of surface tension and fluid dynamics.




Droplet/bubble diameter



Gravitational acceleration



Dimensional constant



Droplet/bubble density



Surrounding fluid density



Surface tension

The Bond number helps determine whether gravitational forces or surface tension forces dominate the behavior of the fluid system. Depending on the value of the Bond number, different flow regimes can be identified:

  • If Bo ≪ 1, surface tension forces dominate over gravitational forces, and the fluid tends to form droplets or maintain a spherical shape. This typically occurs in situations where surface tension is significant relative to gravity, such as small droplets or bubbles.
  • If Bo ≫ 1, gravitational forces dominate over surface tension forces, and the fluid tends to spread out or flow freely. This typically occurs in situations where gravity is significant relative to surface tension, such as large bodies of fluid or fluid flows on inclined surfaces.

The Bond number is commonly used in the analysis of various fluid systems, including droplet formation, bubble dynamics, and capillary flows. It helps engineers and scientists understand and predict the behavior of fluids in different scenarios.

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