Flow-Induced Vibration in a Single Row of Cylinders With p/D = 1.26

2021 ◽  
Author(s):  
Roberta F. Neumeister ◽  
Adriane P. Petry ◽  
Sergio V. Möller
Keyword(s):  
Hot Wire ◽  
Flow Induced Vibration ◽  
Single Row ◽  
Reference Flow ◽  
Wake Interaction ◽  
Hot Wire Anemometry ◽  
Tube Banks ◽  
Comparison Of The Results ◽  
The Impact ◽  
Space Ratio

Abstract Crossflow over a row of cylinders with a close space ratio presents an asymmetric configuration with large and narrow wakes behind the cylinders. The wake interaction can impact the vibration response of the cylinders. In tube banks, the impact results in damages to the equipment. The present experimental study aims to analyze the influence of close space observed in a single row of cylinders on the flow-induced vibration. The study compares a single row with fixed cylinders and a single row with one cylinder free to vibrate. The cylinder free to vibrate is tested in four configurations. The study was conducted with an aerodynamic channel with a cross-section of 0.193 × 0.146 m and smooth cylinders with a diameter of 25.1 mm, space ratio is 1.26. The measurements are executed with hot-wire anemometry and accelerometers, for the cases with one cylinder free to vibrate and with hot-wire anemometry and microphones for the case with all fixed cylinders. The Reynolds number ranges between 1.0 × 104 and 4.5 × 104, obtained with the reference flow velocity, measured with a Pitot tube, and the cylinder diameter. The comparison between the wake response for single row fixed and single row and free to vibrate are executed using Fourier transform and Wavelet Transform. The comparison of the results with the models presented in the literature to predict the elastic instability of the fluid in a single row of cylinders is performed.

scholarly journals Optimal profile for concave slopes under static and seismic conditions

2016 ◽  
Vol 53 (9) ◽  
pp. 1522-1532 ◽  
Author(s):  
Farshid Vahedifard ◽  
Shahriar Shahrokhabadi ◽  
Dov Leshchinsky
Keyword(s):  
Limit Equilibrium ◽  
Stable Configuration ◽  
Preliminary Evaluation ◽  
Construction Technology ◽  
Stability Of Slopes ◽  
Optimal Profile ◽  
Stabilized Soil ◽  
The Stability ◽  
Comparison Of The Results ◽  
The Impact

This study presents a methodology to determine the stability and optimal profile for slopes with concave cross section under static and seismic conditions. Concave profiles are observed in some natural slopes suggesting that such geometry is a more stable configuration. In this study, the profile of a concave slope was idealized by a circular arc defined by a single variable, the mid-chord offset (MCO). The proposed concave profile formulation was incorporated into a limit equilibrium–based log spiral slope stability method. Stability charts are presented to show the stability number, MCO, and mode of failure for homogeneous slopes corresponding to the most stable configuration under static and pseudostatic conditions. It is shown that concave profiles can significantly improve the stability of slopes. Under seismic conditions, the impact of concavity is most pronounced. Good agreement was demonstrated upon comparison of the results from the proposed method against those attended from a rigorous upper bound limit analysis. The proposed methodology, along with recent advances in construction technology, can be employed to use concave profiles in trenches, open mine excavations, earth retaining systems, and naturally cemented and stabilized soil slopes. The results presented provide a useful tool for preliminary evaluation for adopting such concave profiles in practice.

Hot-wire Anemometry in Low-Density Flows

AIAA Journal ◽  
1971 ◽  
Vol 9 (10) ◽  
pp. 2019-2027 ◽  
Author(s):  
E. M. SCHMIDT ◽  
R. J. CRESCI
Keyword(s):  
Low Density ◽  
Hot Wire ◽  
Hot Wire Anemometry

Deceleration of sliding motorcycles (mainly scooters) in accident reconstructions

2017 ◽  
Vol 232 (7) ◽  
pp. 866-876 ◽  
Author(s):  
Carlo Cialdai ◽  
Dario Vangi ◽  
Antonio Virga
Keyword(s):  
Urban Areas ◽  
Test Session ◽  
Road Accidents ◽  
Factors Affecting ◽  
Different Types ◽  
Energy Dissipated ◽  
Comparison Of The Results ◽  
Two Wheeler ◽  
The Impact ◽  
Good Agreement

This paper presents an analysis of the situation in which a two-wheeler (i.e. a motorcycle, where the term motorcycles includes scooters) falls over to the side and then successively slides; this typically occurs in road accidents involving this type of vehicle. Knowing the deceleration rate of the sliding phase allows the kinetic energy dissipated and the speed of the motorcycle just before the fall to the ground to be calculated. These parameters are very important in the analysis and reconstruction of accidents. The work presented in this paper was developed in two experimental test sessions on fully faired motorcycles which are mainly of the scooter type and widely used in urban areas. In the first session, sliding tests were carried out, with the speed in the range 10–50 km/h, on three different types of road surface. Analysis of the evidence allowed the dissipative main phases of motion of the motorcycle (the impact with the ground, the rebounds and the stabilized swiping) to be identified and some factors affecting the phenomenon to be studied. The coefficient of average deceleration was calculated using two typical equations. The second test session consisted of drag tests. In these tests, the motorcycle, which had previously laid on its side, was dragged for a few metres at a constant speed of about 20 km/h, while the drag force was measured. A comparison of the results obtained in these tests with those obtained in the sliding tests yielded very good agreement in the coefficients of deceleration.

Combined Simultaneous Flow Visualization/Hot-Wire Anemometry for the Study of Turbulent Flows

1980 ◽  
Vol 102 (2) ◽  
pp. 174-182 ◽  
Author(s):  
R. E. Falco
Keyword(s):  
Pressure Gradient ◽  
Flow Visualization ◽  
Turbulent Flows ◽  
Unsteady Flows ◽  
Gradient Flows ◽  
Hot Wire ◽  
Visual Patterns ◽  
Favorable Pressure Gradient ◽  
Hot Wire Anemometry ◽  
Scattering Light

The measurement of coherent motions in turbulent and unsteady flows is discussed. A technique which discriminates these motions based upon the patterns they create by scattering light from a fog of tiny oil drops is described. It is shown that hot-wire anemometry can be used in this oil fog so that hot-wire data can be conditionally sampled to the visual patterns, giving directly interpretable measures of the importance of the selected features. The three-dimensionality of the coherent motions can also be directly accounted for, using mutually orthogonal sheets of light. Results of step flows, and zero and favorable pressure gradient flows are described.

Analysis of hot-wire anemometry data obtained in a synthetic jet flow

2004 ◽  
Vol 28 (4) ◽  
pp. 265-272 ◽  
Author(s):  
S.G. Mallinson ◽  
J.A. Reizes ◽  
G. Hong ◽  
P.S. Westbury
Keyword(s):  
Jet Flow ◽  
Synthetic Jet ◽  
Hot Wire ◽  
Hot Wire Anemometry

New Experimental Data and Analysis for Two-Phase Flow-Induced Vibration of Tube Bundles: Preliminary Results

2003 ◽  
Author(s):  
Deepanjan Mitra ◽  
Vijay K. Dhir ◽  
Ivan Catton
Keyword(s):  
Two Phase Flow ◽  
Structural Parameters ◽  
Cross Flow ◽  
Instability Criterion ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Void Fractions ◽  
Comparison Of The Results ◽  
Square Array

In the past, fluid-elastic instability in two-phase flow has been largely investigated with air-water flow. In this work, new experiments are conducted in air-water cross-flow with a fully flexible 5 × 3 normal square array having pitch-to-diameter ratio of 1.4. The tubes have a diameter of 0.016 m and a length of 0.21 m. The vibrations are measured using strain gages installed on piano wires used to suspend the tubes. Experiments are carried out for void fractions from 0%–30%. A comparison of the results of the current tests with previous experiments conducted in air-water cross-flow shows that instability occurs earlier in a fully flexible array as compared to a flexible tube surrounded by rigid tubes in an array. An attempt is made to separate out the effects of structural parameters of three different experimental datasets by replotting the instability criterion by incorporating the instability constant K, in the reduced velocity parameter.

scholarly journals Poisoning of Dogs in the Republic of Macedonia- Pathomorphological Changes and the Impact on Animal Welfare

2018 ◽  
Vol 41 (2) ◽  
pp. 203-207
Author(s):  
Ivica Gjurovski ◽  
Monika Dovenska ◽  
Aleksandar Janevski ◽  
Trpe Ristoski
Keyword(s):  
Gastrointestinal Tract ◽  
Histopathological Examination ◽  
Unknown Origin ◽  
Wild Animals ◽  
Histopathological Changes ◽  
Animal Suffering ◽  
Republic Of Macedonia ◽  
The Republic ◽  
Comparison Of The Results ◽  
The Impact

Abstract The illegal poisoning of dogs and other domestic and wild animals presents a worldwide problem causing animal suffering and R. Macedonia is not an exeption. The goal of this study is to make a comparison of the results from the histopathological examination conducted among poisoned dogs in the Republic of Macedonia. Morphological and histopathological changes in poisoned dogs were investigated for a period of 10 years. The examination was performed on 31 dogs, 13 of which were home kept, 7 were street dogs and 11 of unknown origin. The most significant necropsy findings concerned the inflammatory and necrotic processes of the gastrointestinal tract. The histopathological changes were mainly located in the kidneys, stomach, intestines and the lungs.

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