REYNOLDS-NUMBER DEPENDENCE OF THE DRAG COEFFICIENT FOR LAMINAR-FLOW THROUGH FINE-SCALE PHOTOETCHED SCREENS

The laminar steady flow downstream of fine-mesh screens is studied. In stead of woven-wire screens, high-uniformity screens are fabricated by photoetching holes into 50.8 mum thick Inconel sheets. The resulting screens have minimum wire widths of 50.8 mum and inter-wire separation s of 254 mum and 318 mum for the two screens examined. A flow facility has been constructed for experiments with these screens. Air is passe d through the screens at upstream velocities yielding wire width Reyno lds numbers from 2 to 35. To determine the drag coefficient, pressure drops across the screens are measured using pressure transducers and m anometers. Three-dimensional flow simulations are also performed. The computational drag coefficients consistently overpredict the experimen tal values. However, the computational results exhibit sensitivity to the assumed wire cross section, indicating that detailed knowledge of the wire cross section is essential for unambiguous interpretation of experiments using photoetched screens. Standard semi-empirical drag co rrelations for woven-wire screens do not predict the present experimen tal results with consistent accuracy.