Water hammer with column separation: A historical review

Column separation refers to the breaking of liquid columns in fully filled pipelines. This may occur in a water-hammer event when the pressure in a pipeline drops to the vapor pressure at specific locations such as closed ends, high points or knees (changes in pipe slope). The liquid columns are separated by a vapor cavity that grows and diminishes according to the dynamics of the system. The collision of two liquid columns, or of one liquid column with a closed end, may cause a large and nearly instantaneous rise in pressure. This pressure rise travels through the entire pipeline and forms a severe load for hydraulic machinery, individual pipes and supporting structures. The situation is even worse: in one water-hammer event many repetitions of cavity formation and collapse may occur. This paper reviews water hammer with column separation from the discovery of the phenomenon in the late 19th century, the recognition of its danger in the 1930s, the development of numerical methods in the 1960s and 1970s, to the standard models used in commercial software packages in the late 20th century. A comprehensive survey of laboratory tests and field measurements is given. The review focuses on transient vaporous cavitation. Gaseous cavitation and steam condensation are beyond the scope of the paper. © 2005 Elsevier Ltd. All rights reserved.A. Bergant, A.R. Simpson, and A.S. Tijsselinghttp://www.elsevier.com/wps/find/journaldescription.cws_home/622877/description#descriptio

Outcome of ureteral distensibility on the success of ureteroscopy: A prospective hospital-based descriptive study

AbstractIntroduction“Difficult ureter” is a known problem that increases the complications during ureteroscopy.ObjectiveTo categorize ureters according to their distensibility, and to determine whether ureteric distensibility is associated with the success of ureteroscopy and its complications.Subjects and methodsBetween January 2010 and September 2012, we tested ureteral distensibility in 306 patients who had a unilateral single radiopaque ureteral stone, 6–20mm in diameter. Ureteral distensibility was classified into two categories according to the maximum size of a ureteral dilator that could be introduced before ureteroscopy: non-distensible ureters, which admitted a dilator up to 10 Fr and distensible ureters, which admitted a dilator >10 Fr. Correlations between distensibility and the success rate and complications of ureteroscopy were determined.ResultsOverall, 102 patients (33.3%) had non-distensible ureters and 204 (66.7%) had distensible ureters. Distensibility was correlated with the success of ureteroscopy because initial ureteroscopy failed in 38.2% of non-distensible ureters. Ureteroscopy was successful in all distensible ureters. The incidence of ureteric injury was higher in non-distensible ureters than in distensible ureters.ConclusionsOur results suggest that ureteric distensibility should be tested before ureteroscopy. Primary ureteroscopy is recommended in distensible ureters because of its low complication rates and favorable outcome. Pre-stenting may be necessary before ureteroscopy in non-distensible ureters; secondary ureteroscopy may be safer and more feasible in these settings

Delineation of the subsurface boundary between the Central and Southern Eastern Desert, Egypt

The shear zone characterization is a substantial task for understanding the influencing tectonic movements. In this study, an integrated approach of remote sensing and aeromagnetic data is introduced to imagine and trace the subsurface shear zone between the Central (CED) and Southern (SED) domains of the Egyptian Eastern Desert in comparison with the previously proposed approaches mainly using only surface criteria. To produce an enhanced geological map reflecting the different lithological units along both sides of the surficial shear zone, Landsat-8 images are processed and interpreted using False Color Composite (FCC), Color Ratio Composites (CRC). Moreover, the associated lineaments and their trends are extracted from Digital Elevation Model (DEM) data using the lineaments extraction approaches. For delineating the subsurface structures pattern and tracking the probable subsurface CED/SED boundary, aeromagnetic datasets are reduced to magnetic pole (RTP) and, then, interpreted by applying significant techniques comprising upward continuation, Gaussian separation filter, horizontal gradient magnitude (HGM), and tilt derivative angle (TDR). The best path of the shear zone line at depths was imagined; this path agrees with some geologists' opinion regarding the superficial description of the CED/SED separating shear zone. On the other hand, trend analysis was applied on the subsurface and surface data, reflecting a positive matching between the resulting trends from the magnetic and remote sensing data. The NW direction represents both data's major trend and less common NNW NS, NNE, and ENE trends. This relation reflects the extension and effect of the subsurface structures on the surface in the study area