b'Theacquiring an image of a calibration- only the water that was depositedRESULTS AND DISCUSSIONacquisitionsheet with markings of known sizeon the conveyer surface by the fluidThe results of both PIV measurement of PIV dataand spacing to correct the pixel-basednozzle. The collection was achievedregions are joined into a single figure at a range ofimages to real-world dimensions.using a compressed air vacuumfor each setup to facilitate assessment time delaysCross-correlation between the image- tube at 85 psi and outfitted with aof the flow character near the boundary allowedpairs allows determination of displace,commercial shop-vac (Rigid WD1851)layer manipulation device (PIV region accurate PIVand associated velocity, of the 10umwet surface attachment that was1) as well as the interaction region processingtracer particles. The oil-based particlespositioned just above the conveyerbetween the spray and the conveyor for the widewere introduced from one corner ofsurface and spanned the width of(PIV region 2). In Figures 6-14 the PIV range ofthe room until a sufficient nominallythe conveyor. The position of theresults are presented for many of the velocities uniform seed concentration wasvacuum in relation to the fluid nozzleexamined cases, in each figure, the dispersed in the testing room. is shown in Figure 3. The vacuumpresented results elements are:tube was connected directly to the A sample of 200 double-frame imageswet surface attachment and had 3 ftPIV vectors in blue with the were acquired with time delays ofof 1 diameter rigid tubing directingsize relative to the flow velocity 15, 50, and 125 s for each setupthe water and air into a collectionmagnitude. The number of vectors in each region; each batch of 200chamber which contains a fine-fibreis downsampled by 4 for easier instantaneous vector field was averagedfilter to separate the water from theviewing.to provide a single ensemble averageair during the timed collection period.The gray-scale background is flow field. The acquisition of PIV data atThis collection chamber was weighedrepresentative of the velocity a range of time delays allowed accuratebefore and after each test to determinemagnitude.PIV processing for the wide range ofthe amount of water collected, andThe light-gray lines are streamlines velocities, from over 10 m/s near thethe associated volume flow rate. Allcalculated with the u and v conveyor surface, to approximately 0.1water collecting on the upstream facevectors.m/s far from the surface. of the vacuum was collected andThe red lines are the boundary removed to prevent any dripping ontolayer streamwise velocities at each The PIV vector field calculationsthe conveyer and artificially increasing10 mm streamwise increment.used cross-correlations with multi- the collected volume. This collectionThe thick black line is the edge pass constant-size windows of 32x32test was performed for a baseline ofof the boundary layer, i.e. the pixels, 1:1 weight, 75% overlaps, andno mitigation device for 1 minute andboundary layer thickness ()2 passes. These steps provided arepeated 4 times. Then each mitigation vector resolution of 0.36 mm/vectordevice was placed in position andThe results of Figures 6-10 and 0.37 mm/vector in the upstreamthe collection test was repeated.demonstrate the boundary layer and downstream planes, respectively.Finally, due to the spray pattern ofcharacteristics without a spray, and Vector field post-processing utilised athe fluid nozzle being wider than theFigures 11-14 provide the spray velocity median filter to remove and replaceconveyers surface, some amount ofcharacteristics in the downstream PIV vectors with an average 2 standardwater was over-sprayed and neededregion (-187x-128). Note, the with-deviations of its neighbors, and removebe excluded from the volume transferspray results were acquired with no groups with 5 vectors. calculation. During the baseline test,general air seeding, while the no-spray the collection chamber and filter wereresults utilised seeding through the TRANSFER EFFICIENCY (FLUID COLLECTION)used to directly capture the spray outtesting room.METHOD of the nozzle that fell adjacent to the In order to extract transfer efficiencyconveyer for 1 minute. This test wasThe boundary layer thickness,results, fluid collection testing wasrepeated and conducted on both sides conducted with the goal to collectof the conveyer.WORLD PULP&PAPER 77'