A comparison between diffusivities measured by “ring diffusers” and an aerodynamic method

✍ Scribed by C.E. Johnson; J.A. Clark

• Publisher: Elsevier Science
• Year: 1978
• Weight: 704 KB
• Volume: 19
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(78)90023-7

✦ Synopsis

A technique developed by Millington and Peters (1969) was used to estimate diffusivities (K F ) from measurements of the dispersal of a tracer gas from a point source using Fickian diffusion equations. These estimates were found to be about an order of magnitude smaller than aerodynamic diffusivity measurements (KM). The difference was consistent with the increase in the effective diffusivity with distance from the source predicted by a statistical theory for homogeneous, isotropic turbulence.

The potential of the "ring diffuser" technique is limited because the relation between K F and other diffusivities is expected to vary with height and turbulent regime. The chief advantage of the method is its accuracy in slow windspeeds, and it could be useful where other techniques fail.