An aerosol particle of characteristic size D_p moves in an airflow of characteristic length L and characteristic velocity V. The characteristic time required for the particle to adjust to a sudden change in air speed is called the particle relaxation time τ_p, Verify that the primary dimensions of τ_p are time. Then create a dimensionless form of τ_p, based on some characteristic velocity V and some characteristic length L of the airflow (Fig. P7–103). What established dimensionless parameter do you create?

FIGURE P7–103

Transcribed Image Text:

P. μl -L- Р PpD2 18μ V -D₂- Pp