Marangoni number

The Marangoni number (Ma) is a dimensionless number named after Italian scientist Carlo Marangoni. The Marangoni number may be regarded as proportional to (thermal-) surface tension forces divided by viscous forces. It is – for example – applicable to bubble and foam research or calculations of cryogenic spacecraft propellant behaviour.

$\mathrm {Ma} =-{\frac {d\gamma }{dT}}{\frac {L\Delta T}{\eta \alpha }}$

• γ: surface tension, (SI units: N/m);
• L: characteristic length, (SI units: m);
• $\alpha$: thermal diffusivity, (SI units: m²/s);
• η: dynamic viscosity, (SI units: kg/(s·m));
• ∆T: temperature difference, (SI units: K).

See also

• Marangoni effect