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6777956 
Journal Article 
Aerodynamic and geometric diameters of airborne particles 
Chen, WN; Fryrear, DW; , 
2001 
1 
Journal of Sedimentary Research
ISSN: 1527-1404
EISSN: 1938-3681 
SEPM-SOC SEDIMENTARY GEOLOGY 
TULSA 
71 
3 
365-371 
WOS:000168458700004 
Settling velocity and aerodynamic equivalent diameter are properties of eolian particles that determine eolian transportation and deposition, This study establishes a relationship between geometric diameter and aerodynamic equivalent diameter. Glass spheres and five natural eolian deposits were dry-sieved to 15 size classes from 10 to 600 mum using an ultrasonic sieve, A vertical settling air tube (VSAT) was used to measure the average settling time and velocity, Terminal settling velocity and aerodynamic diameter were obtained by Stokes' Law and Newton's motion equation. Aerodynamic equivalent diameter varies as a power function of sieve diameter. Aerodynamic diameters are larger than geometric diameters for particles finer than 100 mum and smaller for particles coarser than 100 mum, Air settling decreases the spread of particle sizes as estimated from sieving, A shape factor (psi) is defined to show the relationship between aerodynamic equivalent diameter and geometric diameter. The measured psi varies as a natural logarithmic function of particle Reynolds number, not a constant as the existing literature suggested.