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Galvan, Sergio,Reggio, Marcelo,Guibault, Francois,Solorio, Gildardo Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.4
The effect of the inlet swirling flow in a hydraulic turbine draft tube is a very complex phenomenon, which has been extensively investigated both theoretically and experimentally. In fact, the finding of the optimal flow distribution at the draft tube inlet in order to get the best performance has remained a challenge. Thus, attempting to answer this question, it was assumed that through an automatic optimization process a Genetic Algorithm would be able to manage a parameterized inlet velocity profile in order to achieve the best flow field for a particular draft tube. As a result of the optimization process, it was possible to obtain different draft-tube flow structures generated by the automatic manipulation of parameterized inlet velocity profiles. Thus, this work develops a qualitative and quantitative analysis of these new draft tube flow field structures provoked by the redesigned inlet velocity profiles. The comparisons among the different flow fields obtained clearly illustrate the importance of the flow uniformity at the end of the conduit. Another important aspect has been the elimination of the re-circulating flow area which used to promote an adverse pressure gradient in the cone, deteriorating the pressure recovery effect. Thanks to the evolutionary optimization strategy, it has been possible to demonstrate that the optimized inlet velocity profile can suppress or mitigate, at least numerically, the undesirable draft tube flow characteristics. Finally, since there is only a single swirl number for which the objective function has been minimized, the energy loss factor might be slightly affected by the flow rate if the same relation of the axial-tangential velocity components is maintained, which makes it possible to scale the inlet velocity field to different operating points.
Sergio Galván,Marcelo Reggio,François Guibault,Gildardo Solorio 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4
The effect of the inlet swirling flow in a hydraulic turbine draft tube is a very complex phenomenon, which has been extensively investigated both theoretically and experimentally. In fact, the finding of the optimal flow distribution at the draft tube inlet in order to get the best performance has remained a challenge. Thus, attempting to answer this question, it was assumed that through an automatic optimization process a Genetic Algorithm would be able to manage a parameterized inlet velocity profile in order to achieve the best flow field for a particular draft tube. As a result of the optimization process, it was possible to obtain different draft-tube flow structures generated by the automatic manipulation of parameterized inlet velocity profiles. Thus, this work develops a qualitative and quantitative analysis of these new draft tube flow field structures provoked by the redesigned inlet velocity profiles. The comparisons among the different flow fields obtained clearly illustrate the importance of the flow uniformity at the end of the conduit. Another important aspect has been the elimination of the re-circulating flow area which used to promote an adverse pressure gradient in the cone, deteriorating the pressure recovery effect. Thanks to the evolutionary optimization strategy, it has been possible to demonstrate that the optimized inlet velocity profile can suppress or mitigate, at least numerically, the undesirable draft tube flow characteristics. Finally, since there is only a single swirl number for which the objective function has been minimized, the energy loss factor might be slightly affected by the flow rate if the same relation of the axial-tangential velocity components is maintained, which makes it possible to scale the inlet velocity field to different operating points.
( Claudia Sanna ),( Chiara Giordanino ),( Ilaria Giono ),( Claudio Barletti ),( Arnaldo Ferrari ),( Serafino Recchia ),( Dario Reggio ),( Alessandro Repici ),( Alessandro Ricchiuti ),( Mauro Salizzoni 대한소화기기능성질환·운동학회 2011 Gut and Liver Vol.5 No.3
Background/Aims: Endoscopic retrograde cholangiopancreatography (ERCP) is the standard approach for the management of biliary complications in liver transplant patients; however, its safety and efficacy have not been established in this setting. This study was performed to evaluate the safety and long-term efficacy of ERCP in transplant patients. Methods: The case reports of 1,500 liver transplant patients were reviewed. Orthotopic liver transplantation (OLT) patients were matched 1:2 with non-OLT patients and followed-up for long-term outcome (median, 7.4 years). Results: Of the 1,500 liver transplant patients, 94 (6.3%) underwent 150 ERCPs after OLT. Anastomotic strictures were present in 45 patients, biliary stones in 24, biliary leaks in 7, papillary stenosis in 2, and primary sclerosing cholangitis in 1. An ERCP success rate of 90.7% was achieved; biliary stenting led to resolution of the bile leak in 7/7 (100%) patients, and biliary stones were removed in 21/24 (87.5%) patients. In addition, 34 of 45 patients with anastomotic stricture underwent endoscopic dilation. We obtained complete resolution in 22/34 (64.7%) patients. OLT patients did not show a higher probability of complications (odds ratio [OR], 1.04), of pancreatitis (OR, 0.80) or of bleeding (OR, 1.34). Conclusions: ERCP is safe and effective for the treatment of post-OLT biliary complications, has a low rate of pancreatitis and results in a durable effect. (Gut Liver 2011;5:328-334)