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Effects of Noncircular Inlet on the Flow Structures in Turbulent Jets

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Journal of Applied Mathematics and Physics 2013年第6期1卷 37-42页

作者： Won Hyun Kim Tae Seon Park School of Mechanical Engineering Kyungpook National University Daegu South Korea

Turbulent jet flows with noncircular nozzle inlet are investigated by using a Reynolds Stress Model. In order to analyze the effects of noncircular inlet, the cross section of inlet are selected as circular, square, and equilateral triangular shape. The jet half-width, vorticity thickness, and developments of the secondary flow are presented. From the result, it is confirmed that the secondary flows of square and equilateral triangular nozzle are more vigorous than that of the circular jet. This development of secondary flows is closely related to the variations of vortical motions in axial and azimuthal directions.

关键词： Noncircular Turbulent Jet Jet Half-Width Vorticity Thickness Secondary flows

VISIOMETRICS OF 2D SHOCK-PLANAR S/F/S CURTAIN INTERACTIONS: VORTEX DOUBLE LAYERS, VORTEX PROJECTILES AND DECAYING STRATIFIED TURBULENCE

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Transactions of Nanjing University of Aeronautics and Astronautics 2001年第Z1期18卷 32-38页

作者： Norman J. Zabusky Shuang ZhangLaboratory of Visiometrics and Modeling,Department of Mechanical and Aerospace Engineering Laboratory of Visiometrics and Modeling.Department of Mechanical and Aerospace Engineering Rutgers University P.O. Box 909. Piscataway New Jersey 08855

Vortex double layers (VDLs) and vortex projectiles (VPs) are the essential coherent structures which emerge in the shock excited (s/f/s) planar parallel "curtain" simulations of a 2D shock tube with PPM. These opposite signed layers, formed by shock induced baroclinic deposition of vorticity, "ind" and are strongly affected by secondary reflected shocks and vortex interactions. In our visiometric mode of working, we quantify several of these processes and introduce time epochs to discuss the emerging phenomena and normalizations to scale (collapse) the data at M =1.5 and 2.0. This versatile configuration, easily obtained in the laboratory, allows us to study the formation, evolution and reacceleration of VPs and stratified turbulence and mixing.

关键词： visiometrics accelerated inhornogeneous flows (aifs) Richtmyer-Meshkov shockcurtain baroclinic vorticity generation vortex double layers (VDLs) vortex projectiles (VPs) stratified turbulence

The Quantitative Density Measurement of Unsteady Flow around the Projectile

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Journal of Flow Control, Measurement & Visualization 2019年第2期7卷 111-119页

作者： Yusuke Hirose Kazuki Ishikawa Yoshiyuki Ishimoto Takumi Nagashima Masanori Ota Shinsuke Udagawa Tatsuro Inage Kazuki Fujita Hideki Kiritani Koji Fujita Kiyonobu Ohtani Hiroki Nagai Graduate School of Engineering Chiba University Chiba Japan Aerospace Engineering Course Tokyo Metropolitan College of Industrial Technology Tokyo Japan Department of Mechanical Engineering Shonan Institute of Technology Fujisawa Kanagawa Japan Institute of Fluid Science Tohoku University Sendai Miyagi Japan

Three-dimensional density measurement of unsteady flow field around a sphere is carried out in the ballistic range at Institute of Fluid Science, Tohoku University. Simultaneous multi-angle measurement system using twelve digital cameras is installed in the test chamber of the ballistic range to achieve the three-dimensional density measurement. The Colored-Grid Background Oriented Schlieren (CGBOS) technique using colored-grid background is utilized for the reconstruction of density. The Mach number of the sphere is set to 1.5. The short pulse LEDs to illuminate the backgrounds are also installed in the chamber to capture the unsteady flow field around a flying sphere. Three-dimensional density distribution around a sphere is successfully reconstructed.

关键词： Background Oriented Schlieren Flow Visualization High Speed flows Unsteady Flow Simultaneous Measurement

Development of Upstream Data-Input Models to Estimate Downstream Peak Flow in Two Mediterranean River Basins of Chile

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Open Journal of Modern Hydrology 2014年第4期4卷 132-143页

作者： Roberto Pizarro-Tapia Rodrigo Valdés-Pineda Claudio Olivares Patricio A. González University of Talca Technological Center of Environmental Hydrology (CTHA) Talca Chile University of Arizona Department of Hydrology and Water Resources Tucson USA Ministry of Public Works Water Resources Directorate (DGA) Coyhaique Chile

Accurate flood prediction is an important tool for risk management and hydraulic works design on a watershed scale. The objective of this study was to calibrate and validate 24 linear and non-linear regression models, using only upstream data to estimate real-time downstream flooding. Four critical downstream estimation points in the Mataquito and Maule river basins located in central Chile were selected to estimate peak flows using data from one, two, or three upstream stations. More than one thousand paper-based storm hydrographs were manually analyzed for rainfall events that occurred between 1999 and 2006, in order to determine the best models for predicting downstream peak flow. The Peak Flow Index (IQP) (defined as the quotient between upstream and downstream data) and the Transit Times (TT) between upstream and downstream points were also obtained and analyzed for each river basin. The Coefficients of Determination (R2), the Standard Error of the Estimate (SEE), and the Bland-Altman test (ACBA) were used to calibrate and validate the best selected model at each basin. Despite the high variability observed in peak flow data, the developed models were able to accurately estimate downstream peak flows using only upstream flow data.

关键词： Peak flows Storm Events Flood Forecasting Peak Flow Index Peak Flow Transit Time Linear and No-Linear Models

Numerical Treatment of Nonlinear Third Order Boundary Value Problem

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Applied Mathematics 2011年第8期2卷 959-964页

作者： Pankaj Kumar Srivastava Manoj Kumar 不详

In this paper, the boundary value problems for nonlinear third order differential equations are treated. A generic approach based on nonpolynomial quintic spline is developed to solve such boundary value problem. We show that the approximate solutions of such problems obtained by the numerical algorithm developed using nonpolynomial quintic spline functions are better than those produced by other numerical methods. The algorithm is tested on a problem to demonstrate the practical usefulness of the approach.

关键词： Nonlinear Third Order Boundary Value Problem Nonpolynomial Quintic Spline Draining and Coating flows

Water and the Configuration of Social Worlds: An Anthropological Perspective

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Journal of Water Resource and Protection 2013年第4期5卷 59-66页

作者： Kirsten Hastrup University of Copenhagen Copenhagen Denmark

From an anthropological perspective, water is not only the sine qua non of life in general, it is also seen to configure societies in particular ways, and to generate particular values. This will be substantiated in four moves. First, the hydrological cycle and other elementals of water will be discussed. Second, we shall zoom in on rivers, transforming natural resources and social communities as they bend and twist. Third, we shall discuss artificially established canals, emulating natural flows, but having their own long-term social and political implications. Fourth, we shall focus on wells, providing nodal points of social life and potential conflict. The article ends with some observations on water as a theory-machine.

关键词： Sociality of Water Rivers Contested flows Canals Wellsprings Virtual Water

Solid Transfer in Low Flow Sewers, the Distance Travelled So Far Is Not Enough

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Journal of Environmental Protection 2019年第2期10卷 164-207页

作者： Rodney McDermott Alan Strong Philip Griffiths Belfast School of Architecture and the Built Environment Ulster University Belfast Northern Ireland

Sewer blockages are on the increase whilst water closet (WC) flush volumes are on the decrease. Furthermore, Water UK reported figures show that the actual number of properties affected by sewer flooding is on the rise. Sewer blockages can lead to sewer flooding of homes and collapse of sewers which impact negatively on social, economic and environmental factors, and therefore, they are not sustainable. Water conservation is required due to water stress but reduced water use results in less water to waste, which in turn reduces solids’ transfer in sewers. When considering reducing water usage through water conservation, these savings could be cancelled out by an increased population and the situation exacerbated by the impacts of climate change. There are issues in relation to varying design methods, a reliance on engineering judgement in sewer design, uncertainty relating to future water stress, and a lack of cross disciplinary design decision-making. Public health engineering solutions are needed to reduce the number of sewer blockages and the environmental impact of sewer flooding. This paper examines the fundamental research that have been carried out in the area of “solid transfer in sewers” resulting from “less water to waste” since the mid-20th Century. Contrary to existing literature, this paper identifies that, now more than ever, this type of research is needed to deal with the increased need for water conservation. To judge that solid transfer research is complete can be compared to supporting a statement that “water conservation is complete”.

关键词： Sewer Blockages Water Conservation Low flows in Sewers

The Habitat Structure of Lukanga Ramsar Site in Central Zambia: An Understanding of Wetland Ecological Condition

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Open Journal of Ecology 2017年第6期7卷 406-432页

作者： Harry Chabwela Chansa Chomba Loyd Thole Department of Biological Sciences University of Zambia Lusaka Zambia School of Agriculture and Natural Resources Disaster Management Training Centre Mulungushi University Kabwe Zambia Zambia Environmental Management Authority Ministry of Lands and Natural Resources Lusaka Zambia

A field survey was carried out to determine the vegetation structure of the Lukanga Swamp Ramsar site in central Zambia. The aim of the study was to identify the different vegetation communities, species composition and distribution patterns for improved habitat management. Sampling was conducted in all recognizable vegetation communities. The results of the survey showed that the swamp was a littoral palustrine wetland predominantly characterized by the dominance of Leersia hexandria Swartz (42.02%), Typha capensis Rohrb (62.43%), Phragmites australis (Cav.) Trin. ex Steud (33.61%), Aeschynomeme fluitans Peter (31.58%) and Polygonum senegalense Meisn (48.8%). The occurrence of Vossia cuspidata Griff and Cyperus papyrusL was restricted to small and isolated locations. Short Termitaria was generally covered by Acrocerus macrum Stapf (35.25%) while tall Termitaria was dominated by Panicum maximum Jacq. (26.00%). The most important woody plant species included Combretum ghasalense Engl. et Diels (I. V = 62.88), Pseudolachnostylis maprouneifolia Pax ((I. V = 90.48), Albizia adianthifolia (Schmacher) W.F. Wight (I. V = 135.63) Isoberlinia angolensis Hyle and Brenan (I. V = 87.25). The current structure of the hydrophytes composition observed in this study was an indication of a generally silting wetland, while the dominant occurrence of understorey woody plants in the surrounding vegetation signified degraded miombo vegetation. It was concluded that the ecological status of wetland habitat was potentially threatened by mainly anthropogenic activities such as;wildfires, and unsustainable exploitation of surrounding vegetation. Further research is required to examine water flows, eutrophication and the long-term effects of deforestation on the ecological functioning of the wetland.

关键词： Aquatic Macrophytes Wetland Habitat Brachystegia Woodland Palustrine Swamp Sedimentation Environmental flows Wetland Fires and Overexploitation

The Oscillatory Motion of Oldroyd-B Fluid by Incorporating Some of the Mechanical Factors

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Journal of Applied Mathematics and Physics 2017年第12期5卷 2402-2410页

作者： Amir Khan Gul Zaman Yongjin Li Saeed Ahmad Altaf Hussain Department of Mathematics and Statistics University of Swat Khyber Pakhtunkhwa Pakistan Department of Mathematics University of Malakand Chakdara Dir (Lower) Khyber Pakhtunkhwa Pakistan Department of Mathematics Sun Yat-sen University Guangzhou China

The aim of this paper is to present a numerical study of oscillatory motion of Oldroyd-B fluid in a uniform magnetic field through a small circular pipe. First, we derive the orientation stress tensor by considering the Brownian force. Then, the orientation stress tensor is incorporated by taking Hookean dumbbells on Brownian configuration fields in the Oldroyd-B model. The Oldroyd-B model is then reformulated coupled with the momentum equation and the total stress tensor. Finally, we analyze the orientation stress tensor in the pipe by the numerical simulations of the model and showed that the effect of orientation stress tensor is considerable although the Brownian force is sufficiently small.

关键词： Oldroyd-B Fluid Brownian Force Finite Difference Oscillatory flows