The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains. Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph. However, less attention has been paid to the pantograph recess compared with the pantograph. In this paper, the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess, which is represented as a rectangular cavity and numerically investigated at 1/10 scale. Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation, and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction. The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications, and consequently, the noise radiated from the cavity is reduced. Furthermore, effects of the rounded cavity edges on the flow and noise of the pantographs (one raised and one folded) are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges. Different train running directions are also considered. Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph, whereas the flow velocity in the cavity is slightly increased by the rounding. Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph, whereas weaker fluctuations are found on the panhead of the raised pantograph. This study shows that by rounding the cavity edges, a reduction in radiated noise at the side and the top receiver positions can be achieved. Noise reductions in the other directions can also be found.
Anomalous union between the pancreatic and biliary systems (APBDU) has been reported to produce choledochal cyst. The aim of this experiment was to evaluate the role of sphincteroplasty to adverse effect of APBDU in an animal model. Twelve mongrel puppies were randomly divided into a control group (n = 5) and an experimental group (n = 7). A well-established model of APBDU was produced in both groups. Transduodenal sphincteroplasty was performed only on the experimental group. For all animals, serial chemical analyses of serum were performed, and biliary tree sizes were measured by magnetic resonance cholangiography 2.5 months after the experimental surgery. At the time of animal sacrifice, 3 months after the experimental surgery, operative cholangiography was performed, and bile juice and tissues were obtained for chemical analysis and histologic examination. Dilatation of the bile duct and thickening of the wall of the bile duct were observed less frequently in the experimental group than in the control group. There were no significant differences found in pancreatic enzyme activity in the bile juice between the two groups. Denudation of the mucosa was the predominant mucosal change seen in the experimental group, while epithelial hyperplasia was the predominant mucosal change found in the control group. Our experiment shows that sphincteroplasty is not effective to prevent the pancreaticobiliary reflux, but may be effective to reduce the degree of both bile duct dilatation and mural thickening in the APBDU puppy model.
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