EXPERIMENTAL CONSIDERATIONS FOR THE STUDY OF CONTAMINANT DISPERSION NEAR THE BODY

Experimental considerations are discussed for conducting controlled st udies of the dispersion of contaminants released near a mannequin. A 1 83 cm X 183 cm cross section wind tunnel was modified to study the low velocity range of 10 to 100 cm/sec (20 to 200 ft/min). Installation o f a removable biplanar slat grid produced turbulent intensities up to 15%. The results of validation testing for selected experimental compo nents are reported including (1) a minimum, unambiguous velocity measu rement capability of 2.0 cm/sec (4.0 ft/min); (2) a minimum required i ntegration interval for velocity and contaminant measurements of at le ast 3 min; (3) a determination that smoke streamline plume settling ma y be a problem at velocities less than or equal to similar to 15 cm/se c (similar to 30 ft/min); (4) a determination that a 14% tunnel blocka ge by the mannequin was not of consequence for frontal measurements; a nd (5) a finding that the biplanar grid produced turbulence spectra re presentative of low velocity indoor settings. A deceleration zone was noted that extended 50 cm upstream from the mannequin, with freestream velocities reduced 50 to 60%, 2.5 cm from the chest. A contaminant tr acer released as a point source 60 cm upstream typically dispersed lat erally only 10 to 15 cm and diluted by a factor of 10(4) before reachi ng the chest.