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Hydraulic jump and choking of flow in pipe with a change of slope

Journal of Hydrodynamics 2022年第6期34卷 1044-1066页

作者： Rui Zeng S.Samuel Li Department of Building Civil and Environmental EngineeringConcordia UniversityMontrealCanada

This paper investigates hydraulic jumps in sloping pipes by means of wall-resolved large eddy simulation(LES).The purpose is to achieve an improved understanding of jump behaviours driven by pipe discharge and *** LES model predicts the hydraulic jump as a 3-D two-phase flow,with air as the gas phase and water as the liquid *** predictions yield instantaneous velocity and pressure fields as well as fluid volume *** instantaneous flow variables allow ensemble averages,which quantify the internal structures and integral properties of the hydraulic *** predicted instantaneous velocity shows spectra in consistency with the well-known Kolmogorov−5/3 *** ensemble averages of air and water velocities,free-surface profile,roller length and aeration length,compare well with available experimental *** jump behaviours are *** aspects such as free-surface fluctuation and jump-toe oscillation resemble the classical hydraulic jump on horizontal *** like the 3-D distributions of core jet,vorticity and aeration are much more *** on the pipe discharge and slope,the resulting jump can be a complete or an incomplete *** incomplete hydraulic jump causes choked flow *** has severe consequences on drainage conditions in sewer pipes laid on sloping *** paper proposes using the okubo-weiss parameter as a new way to subtly delineate the region of hydraulic *** is much more efficient and less ambiguous,compared with traditional visual inspections.

关键词： Hydraulic jump sloping pipe two-phase bubbly flow large eddy simulation(LES) choking of flow okubo-weiss parameter

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LOW-DEFORMATION VORTICITY AREAS IN SYNOPTIC-SCALE DISTURBANCES FOR TROPICAL CYCLOGENESIS：AN OBSERVATIONAL ANALYSIS

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Journal of Tropical Meteorology 2017年第2期23卷 121-132页

作者：段晶晶吴立广 Pacific Typhoon Research Center and Key Laboratory of Meteorological Disaster of Ministry of Education University of Information Science and Technology Nanjing 210044 China Ningbo Meteorological Observatory of Zhejiang Province Ningbo 315012 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100029 China

It has long been known that incipient tropical cyclones(TCs) always occur in synoptic-scale disturbances or tropical cyclogenesis precursors, and the disturbances can intensify only within a limited area during tropical cyclogenesis. An observational analysis of five tropical cyclogenesis events over the western North Pacific during 11 August to 10 September 2004 is conducted to demonstrate the role of synoptic-scale disturbances in establishing a limited area of low-deformation vorticity for tropical *** analysis of the five tropical cyclogenesis events shows that synoptic-scale tropical cyclogenesis precursors provide a region of low-deformation vorticity, which is measured with large positive values of the okubo-weiss(OW) *** OW concentrated areas are within the tropical cyclogenesis precursors with a radius of about 400-500 km and can be found as early as 72 hours prior to the formation of the tropical depression. When the TCs reached the tropical storm intensity, the concentrated OW is confined to an area of 200-300 radius and the storm centers are coincident with the centers of the maximum OW. This study indicates that the tropical cyclogenesis occurs in the low-deformation 18-72 hours prior to the formation of tropical depressions, suggesting the importance of low-deformation vorticity in pre-existent synoptic-scale disturbances. Although the Rossby radius of deformation is reduced in TC genesis precedes,the reduction does not sufficiently make effective conversion of convective heating into kinetic energy within the low-deformation area. Further analysis indicates that the initial development of four of the five disturbances is coupled with the counterclockwise circulation of the mixed Rossby-Gravity(MRG) wave.

关键词： synoptic-scale disturbances low-deformation vorticity okubo-weiss parameter Rossby radius of deformation

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