The formula for sphericity factor, often denoted by Ψ (Psi), aims to quantify how closely the shape of a particle resembles a perfect sphere. A common simplified formula is:
Ψ = dn / a
Where:
- Ψ represents the sphericity factor.
- dn is the nominal diameter (the diameter of a sphere having the same volume as the particle).
- a is the surface area of the particle.
This formula indicates that the sphericity factor is the ratio of the diameter of a sphere with the same volume as the particle, to the actual surface area of the particle. A sphericity factor of 1 indicates a perfect sphere. Lower values indicate less spherical, more irregular shapes.
