stokes
Diffusivityexact by definition
The stokes is the CGS unit of kinematic viscosity, exactly 10⁻⁴ m²/s, or 1 cm²/s. Water at 20 °C is about 0.01 St, which is why the practical unit everywhere is the centistokes rather than the stokes itself.
Watch out: Kinematic viscosity is dynamic viscosity divided by density, so a stokes is a poise per gram per cubic centimetre. Lubricant grades quoted as "ISO VG 46" refer to a kinematic viscosity of 46 cSt at 40 °C, and comparing that against a dynamic viscosity in centipoise requires the density.
| 1 | 100 |
Where the unit came from
Named for George Gabriel Stokes, whose law for the drag on a sphere is the basis of the falling-ball viscometer and of the settling velocity calculations in water treatment.
One stokes in every diffusivity unit
| 100,000,000 | square micrometer per second (μm²/s) | |
| 3,155.76 | square meter per year (m²/yr) | |
| 100 | square millimeter per second (mm²/s) | |
| 100 | centistokes (cSt) | |
| 93.0002 | square foot per day (ft²/d) | |
| 8.64 | square meter per day (m²/d) | |
| 3.87501 | square foot per hour (ft²/h) | |
| 1 | square centimeter per second (cm²/s) | |
| 1 | stokes (St)this unit | |
| 0.36 | square meter per hour (m²/h) | |
| 0.155 | square inch per second (in²/s) | |
| 0.00107639 | square foot per second (ft²/s) | |
| 0.0001 | square meter per second (m²/s) |
Solvers that use diffusivity