Experimental results for several trashrack models placed in a pressurized rectangular conduit are presented. The tests were performed for both straight and oblique approach flows. Trashrack models of different bar cross-sectional shapes, bar thicknesses, bar depths and bar spacing were studied for a range of velocities. The results indicate that the head loss across the trashrack increases with increasing approach velocity, flow inclination, and blockage ratio. Lower head losses were observed for bars with cross-sectional shape other than rectangular. Results were found to differ only moderately from the previous trashrack energy loss literature based almost entirely on open channel flow experiments. An equation has been developed that well represents the current experimental findings.
An experimental study of turbulent open channel flow near trashrack models is reported. The trashrack models comprised of an array of rectangular bars of identical thickness. The experiments were conducted for a fixed bar depth but different center-to-center spacing, and then for a fixed center-to-center spacing but different bar depths. A high resolution particle image velocimetry (PIV) technique was used to conduct detailed velocity measurements in the streamwise-spanwise planes located at mid-depth of flow. The mean velocity and Reynolds shear stress were then obtained to study the effects of bar spacing and bar depth on the velocity field and head loss. The results demonstrate that the head loss coefficient increases with increasing blockage ratio but decreases slightly when the bar depth is reduced.
RÉSUMÉOn présente une étude expérimentale de l'écoulement turbulent en canal à surface libre près des grilles de modèles. Les grilles de modèles sont ici constituées d'une rangée de barres rectangulaires d'épaisseur identique. Les expériences ont été réalisées, d'une part avec une profondeur fixe des barres mais un espacement différent centre-à-centre, et d'autre part avec un espacement fixe centre-à-centre mais différentes profondeurs de barres. Une technique de vélocimétrie par images de particules (PIV) de haute résolution a été utilisée pour mesurer en détail les vitesses dans des plans parallèles au courant et transversaux situés à mi-profondeur de l'écoulement. La vitesse moyenne et la contrainte de cisaillement de Reynolds ont alors été obtenues pour étudier les effets de l'espacement des barres et de leur profondeur sur le champ de vitesse et la perte de charge. Les résultats montrent que le coefficient de perte de charge augmente avec l'accroissement du rapport de colmatage mais diminue légèrement quand la profondeur de barre est réduite.
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