Kinematic Viscosity of Air Calculator

Kinematic viscosity (͕) represents the ratio of a fluid's dynamic viscosity (ͱ) to its density (͡). The relationship is expressed with the formula: ͕ = ͱ / ͡. To determine dynamic viscosity across various temperatures, the tool uses Sutherland's empirical law, defined as: ͱ = (1.458 × 10^-6 × T^1.5) / (T + 110.4), where T is measured in Kelvin. Additionally, air density is computed using the ideal gas law: ͡ = P / (R × T), incorporating pressure (P) and the specific gas constant for dry air (R).

Let us calculate the kinematic viscosity of air at a standard temperature of 293.15 K (20 °C) and a barometric pressure of 101,325 Pa. First, we find the dynamic viscosity using Sutherland's formula: ͱ = (1.458 × 10^-6 × 293.15^1.5) / (293.15 + 110.4), which yields approximately 1.81 × 10^-5 Pa·s. Next, using the specific gas constant for dry air (287.05 J/kg·K), we compute the density: ͡ = 101325 / (287.05 × 293.15) = 1.204 kg/m³. Finally, dividing dynamic viscosity by density gives the kinematic viscosity: ͕ = (1.81 × 10^-5) / 1.204 = 1.51 × 10^-5 m²/s.

Always input absolute temperature in Kelvin (add 273.15 to your Celsius value) to ensure accurate results from Sutherland's law. Keep in mind that pressure variations significantly impact high-altitude aerodynamic calculations, whereas temperature dominates in standard atmospheric conditions. Verify your units carefully before performing manual cross-checks against the tool.