S = (η·N)/(P)·(R/c)² - dimensionless bearing operating parameter. Low S → thick film, hydrodynamic; high S → thin, boundary.
Formula
$$ S = \frac{\eta N}{P} \left(\frac{R}{c}\right)^2 $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $η$ | Dynamic viscosity | Pa·s | oil |
| $N$ | Shaft speed | rev/s | tachometer |
| $P$ | Specific bearing load | Pa | load / area |
| $R, c$ | Journal radius, radial clearance | mm | bearing |
Sources
- Sommerfeld (1904).