scholarly journals The Theory and Observational Evidence for Streamlets: A New Velocity-Based Feature Model of Jet Streams and Eddies in the Oceans

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Alexander V. Kazansky ◽  
Antonina A. Shupikova
Keyword(s):  
Cross Sections ◽  
Velocity Structure ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Feature Model ◽  
Optimal Interpolation ◽  
Jet Streams ◽  
Synoptic Features ◽  
Parametric Functions ◽  
Oblique Cone

The aim of this study is the verification of a new velocity-based feature model, called streamlets, proposed recently for objective analysis of the three-dimensional velocity structure of jet streams and eddies in the oceans. Streamlets are continuously imbedded shearing vortex solenoids having two forms: cylindrical (for jets) or toroidal (for eddies, considered as self-closed jets). Both these forms comprise stream coordinates based on streamlines of maximum velocity as an axis and vertical velocity cross-sections defined as an oblique cone with elliptical base. Assimilation of velocity measurements is accomplished by fitting this cone to available data using the well-known Nelder-Mead simplex downhill algorithm for finding the minimum of nonlinear parametric functions. Advantages of the streamlet model are discussed emphasizing its functional integrity. The focus is on velocity data assimilation based on coherency of synoptic scale features as opposed to usual pointwise assimilation methods such as averaging or optimal interpolation. Case studies present synoptic features of a different origin and scale including surface-intensified and subsurface baroclinic examples as well as deep barotropic ones demonstrating universality of the model. The theory of streamlets is also addressed in this paper, since it further sustain the streamlet model.

scholarly journals Entropy Wake Law for Streamwise Velocity Profiles in Smooth Rectangular Open Channels

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 654
Author(s):  
Domenica Mirauda ◽  
Maria Grazia Russo
Keyword(s):  
Free Surface ◽  
Cross Sections ◽  
Water Discharge ◽  
Longitudinal Velocity ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Streamwise Velocity ◽  
Open Channels ◽  
Entropy Model ◽  
Modified Entropy

In narrow open channels, the three-dimensional nature of the flow and the transport momentum from the sidewalls to the central region cause the maximum longitudinal velocity to occur below the water surface. The entropy model is unable to accurately describe the velocities near the free surface when the dip phenomenon exists. The present paper proposes a new dip-modified entropy law for steady open channel flows, which consists of three additional terms: the first one similar to Coles’ function; the second one linearly proportional to the logarithmic distance from the free surface; and the third one depending on the cubic correction near the maximum velocity. The validity of the new model was tested on a set of laboratory measurements carried out in a straight rectangular flume with smooth boundaries and for different values of water discharge, bottom slope, and aspect ratio. A detailed error analysis showed good agreement with the data measured through the present research and a more accurate prediction of the velocity-dip-position compared with the one evaluated through the original entropy model. In addition, the modified entropy wake law matched very well with other literature data collected in rectangular cross-sections with different flow conditions.

Three-Dimensional Structure and Evolution of the MJO and Its Relation to the Mean Flow

2014 ◽  
Vol 71 (6) ◽  
pp. 2007-2026 ◽  
Author(s):  
Ángel F. Adames ◽  
John M. Wallace
Keyword(s):  
Cross Sections ◽  
Rossby Waves ◽  
Three Dimensional ◽  
Building Blocks ◽  
Dimensional Structure ◽  
Kelvin Wave ◽  
Mean Flow ◽  
Jet Streams ◽  
Modal Structure ◽  
Wave Trains

Abstract The two leading principal components of the daily 850- minus 150-hPa global velocity potential in the Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) (1979–2011) data are used as time-varying Madden–Julian oscillation (MJO) indices. Regression maps and meridional cross sections based on these indices are used to document the structure and evolution of the zonal wind (u) and geopotential height (Z) anomalies in the MJO cycle. The data are daily, and they are not separated by season. At upper-tropospheric levels the MJO signature is dominated by eastward-propagating planetary wave packets consisting of equatorial Kelvin waves flanked by Rossby waves centered along 28°N/S, for which the westerly jet streams serve as waveguides. At lower-tropospheric levels the pattern more closely resembles the response to a pulsating heat source over the Maritime Continent, where the Andes block the eastward-propagating Kelvin wave pulse. The contrasting upper- and lower-tropospheric patterns are made up of the same building blocks: a deep, baroclinic modal structure with a node at the 400-hPa level, which dominates the tropical signature, and a barotropic residual field consisting mainly of extratropical wave trains oriented along great circles. The extratropical wave trains emanate from the flanking Rossby waves in the baroclinic modal structure. The strongest of them, which resembles the Pacific–North America (PNA) pattern, extracts kinetic energy from the climatological-mean flow in the jet exit region. At other longitudes the jet stream seems to act as a barrier to the poleward propagation of MJO-related wave activity.

Experimental and Theoretical Study of the Swirling Flow in Centrifugal Compressor Volutes

1990 ◽  
Vol 112 (1) ◽  
pp. 38-43 ◽  
Author(s):  
R. A. Van den Braembussche ◽  
B. M. Ha¨nde
Keyword(s):  
Centrifugal Compressor ◽  
Cross Sections ◽  
Swirling Flow ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Three Dimensional Flow ◽  
Static Pressure Distribution ◽  
Swirl Velocity ◽  
Isentropic Flows ◽  
Operating Points

Measurements of the three-dimensional flow in a simplified model of a centrifugal compressor volute at design and off-design operation are presented. A nearly constant swirl velocity is observed near the walls and a forced vortex type of flow is observed in the center. This velocity distribution is almost identical at all cross sections and all operating points. An explanation is given on how this swirl distribution results from the specific way a volute is filled with fluid. The throughflow velocity component shows a large crosswise variation. A minimum or maximum velocity is observed at the volute center depending on the operating point. A simple analytic model, based on the radial equilibrium of forces, is described. Calculations for isentropic flows reveal the relation between the swirl distribution and the large increase of throughflow velocity toward the center. This explains why volutes should be designed with negative blockage. Nonisentropic calculations, using the experimental loss distribution, correctly reproduce the measured throughflow velocity and static pressure distribution.

scholarly journals A Study of the Formation of Velocity Counter Lines and Secondary (Spiral) Flows in Different Cross Sections of Divergent, Convergent and Uniform Arcs

2017 ◽  
Vol 7 (1) ◽  
pp. 1391-1397
Author(s):  
A. Liaghat ◽  
N. Tavanpour
Keyword(s):  
Mechanical Properties ◽  
Numerical Model ◽  
Flow Field ◽  
Cross Sections ◽  
Numerical Models ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Measured Data ◽  
Spiral Flow ◽  
Water Level Variations

The mechanical properties of flow are very complex in channel arcs. Therefore, dynamic numerical models of fluids are considered effective tools in predicting such flow fields. In this study, the numerical model was validated by the measures of a uniform U-shaped arc with a width of 0.6 meter. Then two similar U shaped arcs, divergent and convergent, were simulated by a three-dimensional numerical model with variable widths from 0.6 to 0.75 meters and 0.6 to 0.45 meters. Validating the numerical model by measured data in the uniform 180-degree arc showed that the model can simulate the flow field in the uniform arc very well. Results regarding several parameters such as rout of maximum velocity, maximum velocity line, water level variations, power of spiral flow, existence of a rotating cell are stated and discussed.

Geological Field Sketches and Illustrations

2019 ◽  
Author(s):  
Matthew J. Genge
Keyword(s):  
Cross Sections ◽  
Earth Science ◽  
Three Dimensional ◽  
Worked Examples ◽  
Scientific Publications ◽  
Thin Sections ◽  
Geological Features ◽  
Different Types ◽  
The Subject

Drawings, illustrations, and field sketches play an important role in Earth Science since they are used to record field observations, develop interpretations, and communicate results in reports and scientific publications. Drawing geology in the field furthermore facilitates observation and maximizes the value of fieldwork. Every geologist, whether a student, academic, professional, or amateur enthusiast, will benefit from the ability to draw geological features accurately. This book describes how and what to draw in geology. Essential drawing techniques, together with practical advice in creating high quality diagrams, are described the opening chapters. How to draw different types of geology, including faults, folds, metamorphic rocks, sedimentary rocks, igneous rocks, and fossils, are the subjects of separate chapters, and include descriptions of what are the important features to draw and describe. Different types of sketch, such as drawings of three-dimensional outcrops, landscapes, thin-sections, and hand-specimens of rocks, crystals, and minerals, are discussed. The methods used to create technical diagrams such as geological maps and cross-sections are also covered. Finally, modern techniques in the acquisition and recording of field data, including photogrammetry and aerial surveys, and digital methods of illustration, are the subject of the final chapter of the book. Throughout, worked examples of field sketches and illustrations are provided as well as descriptions of the common mistakes to be avoided.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

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