1. Aschematic of the facility used in the present investigation is shown in Fig. 2. Air at ambient conditions was the working fluid, supplied to the facility from a controllable "wind generator". A settling chamber, fitted with screens and a honeycomb section, was used to settle and condition the incoming air before this air entered the test section through a contoured nozzle. Two steel pipes having internal diametersof 20mm and 10mm madeup the test section, resultingin a contraction area ratio (upstreamto-downstream cross sectional area) of nc= 4. The length of the upstream pipe was 5m. The upstream flow was artificially perturbed by using 1-mm-thick brass rings, having internal diameters ranging from 10 mmto 19mm. The ringswereplaced at alocation 50 diameters downstreamofthe pipeinlet and 200di-ameters upstream oxthe contraction. The resulting trip-blockageratiofrs: oftrip blockageareato pipe cross-sectional areaj was 0 -10% to /3-75%. The downstreampipe section waslong enough (200 diameters) to ensure total recovery from the contraction and full redevelopment under all the flow conditions investigated.
2. Id) 0