A Numerical Study of Calm Air Sampling with a Blunt Sampler

Abstract

It is found that in the case of upwards sampling the bluntness of the sampler only has a significant effect upon aspiration for large sampling velocities, values that would not generally be physically realistic. In the case of downwards sampling an important nondimensional quantity, B 2 R C , is identified, where B represents the sampler bluntness and R C represents the gravitational effects. This quantity determines the physical conditions for which aspiration will not occur and also the limiting values of the aspiration efficiency when aspiration does occur. In the case of low sampling velocities a difference is noted between experimental and numerical results for aspiration efficiency raising the need for more experimental data in this area. For both upwards and downwards sampling the semi-empirical models of Su and Vincent (2004b) have been modified to account for the information gained from the study. This is particularly important in the downwards sampling case where the modified model is found to agree particularly well with the results obtained.

On the efficiency and correction of vertically oriented blunt bioaerosol samplers in moving air

“…The aspiration performance of a blunt sampler facing upwards in calm air, i.e., for super-isokinetic sampling, has been investigated by Dunnett et al (2006). The particle Stokes number St accounts for turbulent particle motion, i.e., the inertially dominated behavior of particles in a distorted flow and is defined as:…”

Numerical Study of the RespiCon Sampler Performance in the Calm Air

“…The aspiration efficiency for the twodimensional blunt sampler operating in calm air at horizontal and upward and downward vertical orientations was studied by Chung and Dunn-Rankin (1993). Mathematical model and the results of studies of the spherical sampler operating in the calm air are given by Galeev and Zaripov (2003) and Dunnett et al (2006). The results of experimental studies on the inhalable fraction in slow moving air are given by Schmees et al (2008).…”