scholarly journals Пространственные эффекты при взаимодействии ударной волны с продольным каналом газа пониженной плотности

2018 ◽  
Vol 44 (20) ◽  
pp. 5
Author(s):  
П.Ю. Георгиевский ◽  
В.А. Левин ◽  
О.Г. Сутырин
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Low Density ◽  
Three Dimensional Flow ◽  
Gas Channel ◽  
Cross Section Shape ◽  
Dimensional Interaction ◽  
Section Shape

AbstractThree-dimensional interaction of a shock with lateral low-density gas channel of round, elliptic or rectangular cross-section is numerically studied using Euler’s equations. The structure of formed shock wave precursor is described in detail. Internal shear layer instabilities in three-dimensional flow are shown to develop faster than in axisymmetric case. Moderate amplification of high-pressure jet cumulation effect is noted for elliptic and rectangular channel cases. Dependence of precursor growth rate on cross-section shape is studied. It is found that stretching of cross-section shape significantly increases the duration of linear precursor growth phase.

scholarly journals Designing for People’s Safety on Flooded Streets: Uncertainties and the Influence of the Cross-Section Shape, Roughness and Slopes on Hazard Criteria

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2119
Author(s):  
Luís Mesquita David ◽  
Rita Fernandes de Carvalho
Keyword(s):  
Cross Section ◽  
Overland Flow ◽  
Rectangular Cross Section ◽  
Safety Hazard ◽  
Cross Section Shape ◽  
Section Shape ◽  
Flood Flows ◽  
The Cross ◽  
Flooding Risk

Designing for exceedance events consists in designing a continuous route for overland flow to deal with flows exceeding the sewer system’s capacity and to mitigate flooding risk. A review is carried out here on flood safety/hazard criteria, which generally establish thresholds for the water depth and flood velocity, or a relationship between them. The effects of the cross-section shape, roughness and slope of streets in meeting the criteria are evaluated based on equations, graphical results and one case study. An expedited method for the verification of safety criteria based solely on flow is presented, saving efforts in detailing models and increasing confidence in the results from simplified models. The method is valid for 0.1 m2/s 0.5 m2/s. The results showed that a street with a 1.8% slope, 75 m1/3s−1 and a rectangular cross-section complies with the threshold 0.3 m2/s for twice the flow of a street with the same width but with a conventional cross-section shape. The flow will be four times greater for a 15% street slope. The results also highlighted that the flood flows can vary significantly along the streets depending on the sewers’ roughness and the flow transfers between the major and minor systems, such that the effort detailing a street’s cross-section must be balanced with all of the other sources of uncertainty.

Bending properties of three-dimensional honeycomb sandwich structure composites: experiment and Finite Element Method simulation

2017 ◽  
Vol 88 (17) ◽  
pp. 2024-2031 ◽  
Author(s):  
Lihua Lv ◽  
Yaoli Huang ◽  
Jingrui Cui ◽  
Yongfang Qian ◽  
Fang Ye ◽  
...  
Keyword(s):  
Failure Mode ◽  
Cross Section ◽  
Sandwich Structure ◽  
Three Dimensional ◽  
Finite Element Method Simulation ◽  
Cross Section Shape ◽  
Section Shape ◽  
Honeycomb Sandwich ◽  
Bending Failure ◽  
Honeycomb Sandwich Structure

This paper fabricated three-dimensional (3D) honeycomb sandwich structure fabrics with three different cross-section shapes on an ordinary loom by reasonable design with low cost. The 3D honeycomb sandwich structure composites were fabricated by the vacuum assisted resin transfer molding process. Then, the bending properties of 3D honeycomb sandwich structure composites with different cross-section shapes were tested. The results showed that the 3D honeycomb sandwich structure composite with a hexagonal cross-section shape had the maximum load, the 3D honeycomb sandwich structure composite with a triquetrous cross-section shape had the minimum load and the 3D honeycomb sandwich structure composite with a quadrangular cross-section shape had a load between the two. The bending failure mode showed that the 3D honeycomb sandwich structure composite had a typical bending failure mode with compression failure in the front and tensile failure in the back. Finally, the load–displacement curves and failure mode were obtained by FEM (Finite Element Method) simulation with ABAQUS software. The good agreements of comparisons proved the validity of the FEM.

scholarly journals SMEAR LAYER REDUCTION IN ROOT CANALS PREPARED WITH TRIANGULAR AND RECTANGULAR FILES AS EVALUATED BY SCANNING ELECTRON MICROSCOPY

2020 ◽  
pp. 27-30
Author(s):  
MEITA HERISA ◽  
NONI MAHARANI ◽  
RATNA MEIDYAWATI ◽  
DEWA AYU NYOMAN PUTRI ARTININGSIH ◽  
KAMIZAR NAZAR
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Rectangular Cross Section ◽  
Smear Layer ◽  
Canal Wall ◽  
Root Canals ◽  
Cross Section Shape ◽  
Section Shape ◽  
Significant Difference ◽  
Scanning Electron

Objective: Root canal preparation procedures can produce a smear layer when in contact with the root canal wall, which can result in treatmentfailure. As such, the cross-section shape of the file may influence the production of smear layer. In this study, we compared the smear layer productionat the apical third of the root canal wall between files with a triangular or rectangular cross-section shape.Methods: Thirty-two human premolar samples taken from mandibles were divided into two groups whose root canals were prepared using fileswith either a triangular (One Curve®, n=16) or rectangular (Hyflex EDM®, n=16) cross-section shape. After preparation, the root canals were irrigatedwith a combination of 2.5% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA). The smear layers in the apical third of the root canal walls wereobserved using a scanning electron microscope and quantified according to the Foschi scoring system.Results: The Mann–Whitney U-test revealed a significant difference between root canal preparations using the different file shapes. The groupprepared with the triangular file produced lower smear layer scores compared with the group prepared with the rectangular file.Conclusion: Root canal preparations using files with different cross-section shapes (e.g., triangular and rectangular), followed by irrigation with 2.5%NaOCl and 17% EDTA, produced smear layers in the apical third area. However, root canal preparations using files with a triangular cross-sectionshape were shown to reduce smear layer production compared with files with a rectangular cross-section shape

The Computation of Secondary Flow in a 90° Rectangular Cross-Section Bend

1989 ◽  
Vol 203 (6) ◽  
pp. 403-409
Author(s):  
M W Johnson
Keyword(s):  
Cross Section ◽  
Energy Equation ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Three Dimensional Flow ◽  
Time Marching ◽  
Model Equations ◽  
Marching Scheme ◽  
Good Agreement

An explicit time-marching scheme for incompressible inviscid three-dimensional flow is presented. The procedure uses an alternative method to the pseudo compressibility technique and uses the energy equation in place of the continuity equation. Calculations are performed for predicting the strong secondary flows produced when a shear flow enters a 90° bend with a rectangular cross-section. Good agreement is achieved with experimental results and rotation of the Bernoulli surfaces through almost 180° is obtained. Discrepancies in the predictions are largely due to the absence of the viscous terms in the computational model equations.

Measurement and analysis of three-dimensional flow in a centrifugal fan volute with large volute width and rectangular cross-section

2006 ◽  
Vol 220 (2) ◽  
pp. 133-153 ◽  
Author(s):  
D Qi ◽  
Y Zhang ◽  
S Wen ◽  
Q Liu
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Design Method ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Centrifugal Fan ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Flow Parameters ◽  
Flow Phenomena

Among all the elements of a centrifugal fan, the volute is the one that has the lowest flow efficiency. Therefore, improving the performance of the volute is an efficient way to improve the total performance of a centrifugal fan. To contribute a better understanding of the flow structure in the fan volute, the three-dimensional flow in a centrifugal fan volute with a large volute width and rectangular cross-section has been measured in detail by means of five-hole probe at three different flowrates. The time-average swirling and throughflow velocity, static and total pressure distributions on eight cross-sections in the throughflow direction of the volute are presented. The results show the formation and development of the flow in the fan volute of this type, indicate the variation of flow parameters, and discover some peculiar flow phenomena different from the traditional understanding. On the basis of the experimental results, the main hydraulic losses in this kind of fan volute have been preliminarily classified and analysed. The results show that the traditional one-dimensional design method of the volute should be further improved as it is only based on the law of momentum moment conservation and the ideal assumption that the distribution of flow parameters are uniform at the volute inlet.

Investigation on Effect of Centrifugal Compressor Volute Cross-Section Shape on Performance and Flow Field

2012 ◽  
Author(s):  
Mohammad Mojaddam ◽  
Ali Hajilouy Benisi ◽  
Mohammad Reza Movahhedi
Keyword(s):  
Flow Field ◽  
Cross Section ◽  
Centrifugal Compressor ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Model Verification ◽  
Navier Stokes ◽  
Cross Section Shape ◽  
Section Shape

In this article, the effects of volute cross section shape and centroid profile of a centrifugal compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and flow parameters at the inlet and outlet of the centrifugal compressor. The three dimensional flow field model of the compressor was obtained numerically solving Navier-Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement. Modification of a volute was performed by introducing a shape factor for volute cross section geometry. By varying this parameter, new volutes were generated and modeled. The effect of volute cross section shape on compressor pressure ratio and efficiency at design rotational speed were investigated. Also pressure non-uniformity around compressor impeller for new cases was calculated and reported. The results showed how the cross section shape of the volute can influence the compressor characteristics and the non-uniformity of circumferential static pressure as well.

Front Condition for Gravity Currents in Channels of Nonrectangular Symmetric Cross-Section Shapes

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
B. M. Marino ◽  
L. P. Thomas
Keyword(s):  
Froude Number ◽  
Cross Section ◽  
Laboratory Experiments ◽  
Rectangular Cross Section ◽  
Theoretical Models ◽  
Gravity Currents ◽  
Cross Section Shape ◽  
Section Shape ◽  
Front Condition ◽  
Upper Boundary

We study the variation of the Froude number at the front of gravity currents developed in uniform channels whose cross-section shape depends on a parameter usually used in many numerical and theoretical models. The thickness and front velocity of the dense currents running on the bottom are greater for all the cases studied, resulting in a Froude number greater than that corresponding to the rectangular cross-section shape. The light currents developing along the upper boundary show the opposite trend. It is found that the results are not related to the depth and width of the channel. The relationships obtained agree with the results of laboratory experiments in which open and closed channels of different cross-section shapes are used.

scholarly journals On the shape of cicada’s wing leading-edge cross section

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rachel M. Starkweather ◽  
Svetlana V. Poroseva ◽  
David T. Hanson
Keyword(s):  
Cross Section ◽  
Insect Flight ◽  
Leading Edge ◽  
Flight Performance ◽  
Cross Section Shape ◽  
Section Shape ◽  
First Time

AbstractAn important role that the leading-edge cross-section shape plays in the wing flight performance is well known in aeronautics. However, little is known about the shape of the leading-edge cross section of an insect’s wing and its contribution to remarkable qualities of insect flight. In this paper, we reveal, in the first time, the shape of the leading-edge cross section of a cicada’s wing and analyze its variability along the wing. We also identify and quantify similarities in characteristic dimensions of this shape in the wings of three different cicada species.

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