scholarly journals Characteristics of Flow Movement in Complex Canal System and Its Influence on Sudden Pollution Accidents

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Maoyi Luo ◽  
Faxing Zhang ◽  
Zhaoming Song ◽  
Liyuan Zhang
Keyword(s):  
Three Dimensional ◽  
Normal Operation ◽  
Acoustic Doppler Velocimeter ◽  
Canal System ◽  
Cross Sectional ◽  
Head Losses ◽  
Split Ratio ◽  
Canal Systems ◽  
Plane Shape ◽  
Sectional Shape

This study aimed to determine the split ratio, flow-field structure, and effect of different shaped channels to sudden pollution accidents in a generalized complex canal system of a wetland park, both experimentally and numerically. The three-dimensional instantaneous velocities at a typical section of each channel in the generalized model were measured experimentally using an acoustic Doppler velocimeter. The results showed that the split ratio calculation formula of three parallel channels could be derived under the condition of considering the frictional head and the local head losses. The water depth, velocities, and pollutant diffusion were widely influenced by changes in the cross-sectional shape and channel plane shape. The pollutants were trapped by stable vortices and transverse circulation due to shear force and secondary flow, thus delaying the diffusion of pollutants. The research results reported herein can help provide technical support for the normal operation of complex canal systems.

Enamel Crystal Shape: History of an Idea

1987 ◽  
Vol 1 (2) ◽  
pp. 322-329 ◽  
Author(s):  
H. Warshawsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Unit Cell ◽  
Cross Sectional ◽  
Transmission Electron ◽  
History Of ◽  
Sectional Shape ◽  
Imaging Plane

The purpose of this paper is to review evidence which casts doubt on the interpretation universally applied to hexagonal images seen in sectioned enamel. The evidence is based on two possible models to explain the hexagonal profiles seen in mammalian enamel with transmission electron microscopy. The "hexagonal ribbon" model proposes that hexagonal profiles are true cross-sections of elongated hexagonal ribbons. The "rectangular ribbon" model proposes that hexagonal profiles are caused by three-dimensional segments that are parallelepipeds contained in the Epon section. Since shadow projections of such rectangular segments give angles that are inconsistent with the hexagonal unit cell, a model based on ribbons with rhomboidal cut ends and angles of 60 and 120° is proposed. The "rhomboidal ribbon" model projects shadows with angles that are predicted by the unit cell. It is suggested that segments of such crystallites in section project as opaque hexagons on the imaging plane in routine transmission electron microscopy. Morphological observations on crystallites in sections - together with predictions from the hexagonal, rectangular, and rhomboidal ribbon models - indicate that crystallites in rat incisor enamel are flat ribbons with rhomboidal cross-sectional shape. Hexagonal images in electron micrographs of thin-sectioned enamel can result from rhomboidal-ended, parallelepiped-shaped segments of these crystallites projected and viewed as two-dimensional shadows.

scholarly journals Characterization and Control for the Laminar Flow of Liquid Polyurethane System in a Wide Angle Diffuser with Transversely Arrayed Obstacles

2020 ◽  
Vol 10 (4) ◽  
pp. 1228
Author(s):  
Son ◽  
Lee ◽  
Chang
Keyword(s):  
Laminar Flow ◽  
Flow Velocity ◽  
Three Dimensional ◽  
Flow Uniformity ◽  
Cross Sectional ◽  
Lumped Parameter ◽  
Vorticity Vector ◽  
Rms Error ◽  
Sectional Shape ◽  
And Control

In the manufacturing process of hard-board poly-urethane foams, the uniformity is a very important issue for the raw compound of the liquid poly-urethane system flow for the quality control of such products. One of the universal methods to generate more uniform flow is that some obstacles are located inside the diffuser at the end of injector. For the regime of non-Newtonian laminar flow, better flow uniformity can be achieved with the enhancement of mixing in the wake after the resistive obstacles. In this research, the parametric study is made for the gap interval between adjacent obstacle components as well as the cross-sectional shape with a computational fluid dynamics (CFD) technique. The flow fields around circular and elliptic cylinders are visualized for flow velocity and vorticity with the comparison of root-mean-square (RMS) error for the deviation of velocity at the outlet as a lumped parameter to estimate flow uniformity and mixing. When the blockage ratio is fixed 0.3 for the pipe of Reynolds number 58.5 based on its diameter, eliminating the effect of wall boundary ratio with the classical Blasius velocity profile, the RMS error is reduced 77% to 92% from the baseline case in the case of 60%-diameter gaps for the figure of circles and 2:1 longitudinal ellipse, respectively. The flow is visualized around obstacle components with vorticity as well as flow velocity where the three-dimensional components of vorticity vector are also elucidated in physics for the evolution of complex multi-dimensional flow wake.

A Study on the Cross-Sectional Shape of Kerf Cut with Micro Abrasive Air Jet

2012 ◽  
Vol 500 ◽  
pp. 236-241 ◽  
Author(s):  
Quan Lai Li ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Traverse Speed ◽  
Cross Sectional ◽  
Air Jet ◽  
Analysis Technique ◽  
Hard And Brittle Materials ◽  
The Cross ◽  
Sectional Profile ◽  
Sectional Shape

Micro abrasive air jet (MAAJ) cutting is a promising technology for the fabrication of three-dimensional microstructures in hard and brittle materials. In this paper, a study on the cross-sectional shape of the kerf cut with MAAJ is presented. It shows that the machining depth and slope of the sidewall increase with an increase in air pressure, abrasive flow rate and jet incidence angle, while decrease with an increase in nozzle traverse speed. Using a dimensional analysis technique, predictive model for cross-sectional profile is developed. The research results may be meaningful to the highly precision three-dimensional micro-structural cutting.

Non-Contact Area Measurement Techniques for Cross Sectional Properties of Soft Tissues

2003 ◽  
Author(s):  
Dipan Bose ◽  
Jason R. Kerrigan ◽  
Johan Ivarsson ◽  
N. Jane Madeley ◽  
Steve A. Millington ◽  
...  
Keyword(s):  
Cross Section ◽  
Soft Tissues ◽  
Cruciate Ligament ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Area Measurement ◽  
Cross Sectional ◽  
Knee Ligaments ◽  
Human Knee ◽  
Sectional Shape

In this study, a non-contact optical three-dimensional digitization technique is described to account for area measurement problems related to soft tissue. The technique is used to generate digitized models of human knee ligaments (collateral and cruciate ligament bundles). Cross-sectional area of knee ligaments is determined by applying Green’s theorem on data obtained from the digitized models. The surface concavity features of different ligaments shown in this study signify the extent of approximation done by projection based methods. The study also reports the variation in cross-sectional shape of a ligament along its long axis, indicating the importance of deciding the appropriate cross section for stress calculation measurements.

Numerical Simulation of Flow Field Around a Circular-Bladed Butterfly Wind Turbine

2015 ◽  
Author(s):  
Yutaka Hara ◽  
Takahiro Sumi ◽  
Yuhei Matsubara ◽  
Yoshiyuki Yasumoto
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Half Cycle ◽  
Cross Sectional ◽  
Tip Vortices ◽  
Sectional Shape

Three-dimensional computational fluid dynamics (3D-CFD) was performed to simulate the flow field around an aluminum circular-blade butterfly wind turbine, which is a vertical-axis-type turbine with four circular blades and a diameter of 2.06 m. Under the assumption of a loss factor of 0.8 due to a generator and an AC–DC converter, the CFD results agreed with the experimental results. Although tip vortices were observed at the top and bottom portions of the blades, the vorticity intensity was weaker than that of the straight-blade rotor case. In addition, the cross-sectional shape of the tip vortices seemed to be elliptical for circular blades rather than circular as for straight blades. As the tip speed ratio was less than 2, vortices arising from dynamic stall at maximum-radius portions of blades were observed at the downwind half-cycle as well as the upwind half-cycle. A feature of the vortices shed from a circular blade at the downwind half-cycle was the looped shape.

scholarly journals Improving the propulsion speed of a heaving wing through artificial evolution of shape

2019 ◽  
Vol 475 (2221) ◽  
pp. 20180375 ◽  
Author(s):  
Sophie Ramananarivo ◽  
Thomas Mitchel ◽  
Leif Ristroph
Keyword(s):  
Optimization Problems ◽  
Three Dimensional ◽  
Artificial Evolution ◽  
Complex Flows ◽  
Cross Sectional ◽  
Evolutionary Scheme ◽  
Edge Sharpness ◽  
Measured Speed ◽  
And Performance ◽  
Sectional Shape

Aeronautical studies have shown that subtle changes in aerofoil shape substantially alter aerodynamic forces during fixed-wing flight. The link between shape and performance for flapping locomotion involves distinct mechanisms associated with the complex flows and unsteady motions of an air- or hydro-foil. Here, we use an evolutionary scheme to modify the cross-sectional shape and iteratively improve the speed of three-dimensional printed heaving foils in forward flight. In this algorithmic-experimental method, ‘genes’ are mathematical parameters that define the shape, ‘breeding’ is the combination of genes from parent wings to form a daughter, and a wing's measured speed is its ‘fitness’ that dictates its likelihood of breeding. Repeated over many generations, this process automatically discovers a fastest foil whose cross-section resembles a slender teardrop. We conduct an analysis that uses the larger population to identify what features of this shape are most critical, implicating slenderness, location of maximum thickness and fore-aft asymmetries in edge sharpness or bluntness. This analysis also reveals a tendency towards extremely thin and cusp-like trailing edges. These findings demonstrate artificial evolution in laboratory experiments as a successful strategy for tailoring shape to improve propulsive performance. Such a method could be used in related optimization problems, such as tuning kinematics or flexibility for flapping propulsion, and for flow–structure interactions more generally.

Coupled fluid and energy flow in fabrication of microstructured optical fibres

2019 ◽  
Vol 874 ◽  
pp. 548-572 ◽  
Author(s):  
Yvonne M. Stokes ◽  
Jonathan J. Wylie ◽  
M. J. Chen
Keyword(s):  
Surface Tension ◽  
Numerical Method ◽  
Three Dimensional ◽  
External Boundary ◽  
Cross Sectional ◽  
Heating And Cooling ◽  
Standard Problem ◽  
Axial Stretching ◽  
Sectional Shape ◽  
Microstructured Optical Fibres

We consider the role of heating and cooling in the steady drawing of a long and thin viscous thread with an arbitrary number of internal holes of arbitrary shape. The internal holes and the external boundary evolve as a result of the axial drawing and surface-tension effects. The heating and cooling affects the evolution of the thread because both the viscosity and surface tension of the thread are assumed to be functions of the temperature. We use asymptotic techniques to show that, under a suitable transformation, this complicated three-dimensional free boundary problem can be formulated in such a way that the transverse aspect of the flow can be reduced to the solution of a standard Stokes flow problem in the absence of axial stretching. The solution of this standard problem can then be substituted into a system of three ordinary differential equations that completely determine the flow. We use this approach to develop a very simple numerical method that can determine the way that thermal effects impact on the drawing of threads by devices that either specify the fibre tension or the draw ratio. We also develop a numerical method to solve the inverse problem of determining the initial cross-sectional geometry, draw tension and, importantly, heater temperature to obtain a desired cross-sectional shape and change in cross-sectional area at the device exit. This precisely allows one to determine the pattern of air holes in the preform that will achieve the desired hole pattern in the stretched fibre.

scholarly journals Multi-branching three-dimensional flow with substantial changes in vessel shapes

2008 ◽  
Vol 614 ◽  
pp. 329-354 ◽  
Author(s):  
R. I. BOWLES ◽  
N. C. OVENDEN ◽  
F. T. SMITH
Keyword(s):  
Three Dimensional ◽  
Longitudinal Vortex ◽  
Cross Sectional ◽  
Flow Rates ◽  
Relative Flow Rate ◽  
Wide Range ◽  
Flow Through ◽  
Sectional Shape ◽  
Area Expansion ◽  
Reversed Motion

This theoretical investigation of steady fluid flow through a rigid three-dimensional branching geometry is motivated by applications to haemodynamics in the brain especially, while the flow through a tube with a blockage or through a collapsed tube provides another motivation with a biomedical background. Three-dimensional motion without symmetry is addressed through one mother vessel to two or several daughters. A comparatively long axial length scale of the geometry leads to a longitudinal vortex system providing a slender-flow model for the complete mother-and-daughters flow response. Computational studies and subsequent analysis, along with comparisons, are presented. The relative flow rate varies in terms of an effective Reynolds number dependence, allowing a wide range of flow rates to be examined theoretically; also any rigid cross-sectional shape and ratio of cross-sectional area expansion or contraction from the mother vessel to the daughters can be accommodated in principle in both the computations and the analysis. Swirl production with substantial crossflows is found. The analysis shows that close to any carina (the ridge separating daughter vessels) or carinas at a branch junction either forward or reversed motion can be observed locally at the saddle point even though the bulk of the motion is driven forward into the daughters. The local forward or reversed motion is controlled, however, by global properties of the geometry and incident conditions, a feature which applies to any of the flow rates examined.

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