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1

Experimental study on vibration of a rotating pipe in still water and in flow

Geng Xinge, Wu Weiguo, Liu Erpeng, Lin Yongshui, Chen Wei, Rheem Chang-Kyu

Polish Maritime Research

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2023

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nr 1

65--77

EN

To illustrate the vibration characteristics of a rotating pipe in flow, experiments were conducted for a pipe in flow, a rotating pipe in still water and a rotating pipe in flow. For the pipe in flow without rotation, the trajectory diagram is ‘8’ shaped. For the rotating pipe in still water, a multiple frequency component was induced, and a ‘positive direction whirl’ was found. For the flow and rotation, at a flow velocity of 0.46 m/s, the vibration is dominated by the combination of flow and rotation. With an increase in rotating frequency, the trajectory of the rotating pipe varies from an ‘8’ shape to a circular shape and the ‘reverse direction whirl’ is induced, which is different from ‘positive direction’ in still water. The vibration frequency ratio increases uniformly with flow velocity. At a flow velocity of 1.02 m/s, at which the frequency is close to the theoretical natural frequency, the vibration frequency ratio is f*≈1. Predominantly governed by vortex-induced vibration (VIV), the vibration behavior of a rotating pipe subjected to fluid flow conditions has been found to exhibit complete vanishing of whirl. The vibration characteristics of a rotating pipe in flow are studied by the experiments which is benefit for structural drilling design.

2

Minimization of critical flow velocity of aeroelastic energy harvester via delayed feedback control

Sarbinowski Filip, Starosta Roman

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020225

EN

The paper describes the procedure of modelling and optimization of the aeroelastic energy harvester from the point of view of their operation at very low flow velocities. Using analytical solutions of models of different device variants, the relationships between their efficiency and flow velocity were presented. By way of analytical considerations, the conditions for high performance operation of the device have been demonstrated, indicating at the same time the difficulty in maintaining it at low operation velocities. As a solution to the problem, the application of external delayed feedback control was proposed and its effectiveness was demonstrated.

3

Investigation of the Effects of the Incident Flow Angle on Vibration Behavior in Heat Exchanger Tube Bundle

Usman Muhammad, Khushnood Shahab, Nizam Luqman Ahmad, Tanveer Waqas, Shafi Ahmad, Ayub Muhammad, Khan Hassan Farid, Rustam Behzad

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no. 2

186--194

EN

An experimental study on the incident flow angle effects on the vibration behavior was carried out on aluminum tube in parallel triangular tube bundle with P/D ratio of 1.375. Fluid elastic instability is the most fatal mechanism from all the vibration mechanisms and therefore must be dealt with a lot of attention. Experiments were performed on low speed water tunnel with the velocity of water ranges from 0.3 m/s to 0.7 m/s. The experiments were designed in a unique way to study the effects of incident flow angle on the vibration behavior. The monitored tube was mounted flexibly in an array of rigid tubes. The experiments were conducted on a flexible tube for different velocities ranging from 0.3 m/s to 0.7 m/s with different array rotated angles (0 to 90 degrees). It was observed that the vibration level was significantly high at 75 degree configuration as compared to other rotated angle configurations. It was also observed that the damping response is dispersed with all positive values, indicating that there is no instability in the tube.

4

Fretting wear analysis of different tube materials used in heat exchanger tube bundle

Abbas T., Khushnood S., Nizam L. A., Usman M.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no. 4

123--133

EN

Research on heat exchange has been carried out for more than five decades because of its importance in process industries and power generation plants. Heat exchanger experiencing cross flow are vulnerable to flow-induced vibration. This vibration causes the interaction of tubes with the baffle resulting in a fretting wear of the tubes. The present study focuses on fretting wear analysis of different tube materials. Fretting wear tests were performed on aluminum, copper and stainless steel instrumented central tubes against mild steel baffle. For each tube material the tests were performed for three different test durations i.e. 60 minutes, 120 minutes and 180 minutes at a cross flow velocity of 0.55 m/s. It was observed that vibrational amplitude of the flexible test tube is affected by its weight. A scanning electron microscope was used to analyze and measure the sizes of wear scar. The results indicated that wear loss in case of aluminum tube is the highest while that in case of stainless steel tube is the lowest.

5

Parametric vibrations of pipes induced by pulsating flows in hydraulic systems

Łuczko J., Czerwiński A.

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 3

719--730

EN

The paper discusses the model of transverse vibrations of a pipe induced by flow velocity pulsation. The motion is described by a system of two non-linear partial differential equations with periodically variable coefficients. The analysis uses the Galerkin method with orthogonal polynomials as the shape functions. The instability regions are determined by Floquet’s method. The influence of selected parameters on natural frequencies and on the character and level of vibrations is studied. The possibility of the excitation of periodic and quasi-periodic oscillations is demonstrated. The results of theoretical analysis are compared with the experimental data.

6

Vibrations of steel pipes and flexible hoses induced by periodically variable fluid flow

Czerwiński A., Łuczko J

Mechanics and Control

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2012

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Vol. 31, no. 2

63-71

EN

This paper is concerned with the analysis of a model describing the vibrations of simply supported straight pipes conveying periodically pulsating fluid. The vibrations of the hydraulic system are described by a fourth-order partial differential equation, with the inclusion of geometrical non-linearities. Through the application of the Galerkin method, the non-linear problem is reduced to the solution of four ordinary differential equations. The influence of several significant parameters of the model on the rms value of velocity is investigated. The possibility of exciting sub-harmonic and chaotic excitations at certain intervals of excitation frequency and flow velocity is presented.

PL

W pracy poddano analizie model opisujący drgania przegubowo podpartych prostoliniowych przewodów, spowodowane pulsacjami prędkości przepływającej cieczy. Ruch układu opisano równaniem różniczkowym cząstkowym czwartego rzędu, uwzględniającym nieliniowości geometryczne. Wykorzystując metodę Galerkina, zagadnienie rozwiązania równania różniczkowego cząstkowego sprowadzono do problemu analizy układu czterech równań różniczkowych zwyczajnych. Zbadano wpływ wybranych parametrów na wartość skuteczną prędkości drgań. Wykazano możliwość wzbudzania się w pewnych zakresach prędkości przepływu i częstości wymuszenia drgań podharmonicznych i chaotycznych.

7

Wpływ warunków brzegowych na częstości własne i obszary stabilności przewodów hydraulicznych

Łuczko J., Czerwiński A.

Czasopismo Techniczne. Mechanika

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2012

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R. 109, z. 8-M

71--89

PL

W pracy poddano analizie model opisujący drgania poprzeczne przewodu, wywołane pulsacjami prędkości przepływającej cieczy. Ruch układu opisano równaniem różniczkowym cząstkowym o okresowo zmiennych współczynnikach. Analizę przeprowadzono metodą Galerkina z wykorzystaniem wielomianów ortogonalnych jako funkcji kształtu. Do wyznaczenia obszarów niestabilnych zastosowano teorię Floqueta. Zbadano wpływ wybranych parametrów oraz warunków brzegowych na częstości własne układu oraz na zakresy rezonansu parametrycznego.

EN

The paper is concerned with the analysis of a model describing the transverse vibrations induced by periodically variable fluid flow. Motion of the system was described by using partial differential equations with periodically variable coefficients. The analysis was performed by Galerkin method and orthogonal polynomials as shape functions. The instability regions were determined by Floquet theory. The influence of several parameters and boundary conditions on the natural frequencies and the instability regions were investigated.