Experimental evaluation of the velocity fields for local exhaust hoods with circular and rectangular openings

A detailed experimental evaluation of the velocity fields induced in the proximity of local exhaust hoods with circular and rectangular (right quadrilateral) openings is presented. It contains a comprehensive description of the purpose-built test facility, of the measurement instrumentation adopted, and of the experimental procedure in use. Results show that, for a given opening shape, the velocity fields are quite different for flanged or plain hood opening. Fluid-dynamic asymmetries, probably caused by possible instability phenomena (fluid stream attachment) and by the influence of external supports or objects, are also observed. Further work on this topic is presented in a related paper.