An Experimental Study of Flow-Induced Vibration and the Associated Flow Perturbations in a Parallel Triangular Tube Array

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Ahmed Khalifa ◽  
David Weaver ◽  
Samir Ziada
Keyword(s):  
Flow Separation ◽  
Relative Phase ◽  
Interstitial Flow ◽  
Hot Wire ◽  
Flow Induced Vibration ◽  
Perturbation Amplitude ◽  
Flow Perturbation ◽  
Pressure Transducers ◽  
Pitch Ratio ◽  
Vorticity Generation

The results of an experimental investigation of the flow perturbations associated with tube vibrations along the interstitial flow path are presented. A parallel triangular tube array consisting of seven rows and six columns of aluminum tubes with a pitch ratio of 1.54 was studied. Measurements of the interstitial flow perturbations along the flow lane were recorded using a hot-wire anemometer while monitoring the tube vibration in the longitudinal and transverse directions. A single flexible tube located in the third row of a rigid array was instrumented with pressure transducers to monitor the surface pressure variations. The flow perturbation amplitude and phase with respect to the tube vibrations were obtained at a number of locations along the flow lane in the array. The effects of tube vibration amplitude and frequency, turbulence level, location of measurements, and mean gap velocity on the flow perturbation amplitude and relative phase were investigated. It is found that the flow perturbations are most pronounced at the point of flow separation from the tube and decay rapidly with distance from this point. It appears that the time delay between tube vibration and flow perturbation is associated with flow separation and vorticity generation from the vibrating tube.

An Experimental Study of the Phase Lag Causing Fluidelastic Instability in Tube Bundles

2011 ◽  
Author(s):  
Ahmed Khalifa ◽  
David Weaver ◽  
Samir Ziada
Keyword(s):  
Time Delay ◽  
Phase Lag ◽  
Interstitial Flow ◽  
Flow Perturbation ◽  
Pressure Transducers ◽  
Fluid Forces ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
Downstream Flow ◽  
Lift And Drag

The phenomenon of fluidelastic instability forms a major limitation on the performance of tube and shell heat exchangers. It is believed that fluidelastic instability is attributed to two main mechanisms; the first is called the “Damping Mechanism”, while the second is called the “Stiffness Mechanism”. It is established in the literature that in order to model the damping controlled fluidelastic instability, a finite time delay between tube vibration and fluid response has to be introduced. Experimental investigation of the time delay between structural motion and the induced fluid forces is detailed in the present study. A parallel triangular tube array consisting of seven rows and six columns of aluminum tubes is built with a pitch ratio of 1.54. Hot-wire measurements of the interstitial flow perturbations are recorded while monitoring the tube vibrations in the lift and drag directions. Pressure transducers are installed inside the instrumented tubes to monitor the fluid forces. The phase lag between tube vibration and flow perturbation is obtained at different locations in the array. The effect of tube frequency, turbulence level, location of measurements, and mean gap velocity on the relative phase values is investigated. It is found that there are two well-defined regions of phase trends along the flow channel. It is concluded from this study that the time delay between tube vibration and downstream flow perturbation is associated with the vorticity convection downstream, while the time delay for upstream perturbations is associated with the effect of flow separation and vorticity generation which is propagated upstream from the vibrating tube.

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.

Experimental Analysis Methods for Unsteady Flows in Turbomachines

1981 ◽  
Vol 103 (2) ◽  
pp. 415-423 ◽  
Author(s):  
R. Larguier
Keyword(s):  
Experimental Analysis ◽  
Time Pressure ◽  
Unsteady Flows ◽  
Rotor Blades ◽  
Hot Wire ◽  
Short Response Time ◽  
Pressure Transducers ◽  
Direct Measurements ◽  
Hot Film

This paper describes the measuring methods developed at the ONERA Aerodynamics Department for the characterization of unsteady flows in turbomachines. They mainly concern the flow in the rotor, its wake, and boundary layers on stator or rotor blades. The means used consist of: • measurements using pressure probes or short response time pressure transducers, • measurements with hot wire probes or hot film gauges, and • direct, measurements using laser velocimeter.

The vortex-street wakes of vibrating cylinders

1974 ◽  
Vol 66 (3) ◽  
pp. 553-576 ◽  
Author(s):  
Owen M. Griffin ◽  
Steven E. Ramberg
Keyword(s):  
Vortex Formation ◽  
The Body ◽  
Vortex Street ◽  
Longitudinal Vortex ◽  
Cylinder Wake ◽  
Hot Wire ◽  
Formation Region ◽  
Lateral Vibrations ◽  
Vorticity Generation ◽  
Shedding Frequency

The strength (initial circulation) and spacing of vortices in the wake of a circular cylinder have been obtained for conditions under which the body undergoes lateral vibrations. The vibrations of the cylinder were at all times synchronized with those in the wake, thereby suppressing the natural Strouhal frequency in favour of a common synchronized or ‘locked-in’ frequency for the body-wake system. All experiments were performed at a Reynolds number of 144 or 190. An inverse relation between the initial circulation K and the length lF of the vortex formation region was obtained for cylinder oscillations of up to 50% of a diameter, at vibration frequencies both above and below the Strouhal shedding frequency. The initial circulation K of the vortices was increased by as much as 65%, at lF = 1·6 diameters, from the stationary-cylinder value of K corresponding to lF = 3·2d. An increase in the rate A of vorticity generation of 80% from the stationary-cylinder wake value was obtained with the cylinder vibrating at 30% of a diameter and 110% of the Strouhal frequency. Both flow-visualization and hot-wire results show that the lateral spacing of the vortex street decreases as the vibration amplitude of the cylinder is increased, but that the longitudinal vortex spacing is independent of changes in amplitude. The longitudinal spacing, however, varies inversely with the vibration frequency. The street approaches a single line of vortices of alternating sign as the amplitude of vibration approaches values near a full cylinder diameter, and secondary vortex formation at these large amplitudes is associated with the vanishing lateral spacing of the street. Observation of the wake has elucidated the mechanism of vortex formation; the entrainment processes in the formation region have been observed at small intervals over a cycle of the cylinder's motion.

Two-Phase Flow-Induced Vibration of Parallel Triangular Tube Arrays With Asymmetric Support Stiffness

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Paul Feenstra ◽  
David S. Weaver ◽  
Tomomichi Nakamura
Keyword(s):  
Two Phase Flow ◽  
Cross Flow ◽  
Phase Flow ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Tube Arrays ◽  
Tube Bundles ◽  
Pitch Ratio ◽  
Exchanger Tube

Laboratory experiments were conducted to determine the flow-induced vibration response and fluidelastic instability threshold of model heat exchanger tube bundles subjected to a cross-flow of refrigerant 11. Tube bundles were specially built with tubes cantilever-mounted on rectangular brass support bars so that the stiffness in the streamwise direction was about double that in the transverse direction. This was designed to simulate the tube dynamics in the U-bend region of a recirculating-type nuclear steam generator. Three model tube bundles were studied, one with a pitch ratio of 1.49 and two with a smaller pitch ratio of 1.33. The primary intent of the research was to improve our understanding of the flow-induced vibrations of heat exchanger tube arrays subjected to two-phase cross-flow. Of particular concern was to compare the effect of the asymmetric stiffness on the fluidelastic stability threshold with that of axisymmetric stiffness arrays tested most prominently in literature. The experimental results are analyzed and compared with existing data from literature using various definitions of two-phase fluid parameters. The fluidelastic stability thresholds of the present study agree well with results from previous studies for single-phase flow. In two-phase flow, the comparison of the stability data depends on the definition of two-phase flow velocity.

scholarly journals Analysis of the Flow Field in a Radial Compressor

1978 ◽  
Author(s):  
Christian Fradin
Keyword(s):  
Flow Field ◽  
Pressure Field ◽  
Outlet Section ◽  
Inlet Section ◽  
Hot Wire ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Radial Compressor ◽  
Pressure Transducers ◽  
Compressor Inlet

Using pressure transducers and hot wire anemometers, the flow and pressure field in a subsonic centrifugal compressor is analyzed. Detailed pressure, velocity, and flow angle maps are given for the compressor inlet section, along the shroud, in the outlet section of the rotor, and also in the vaneless diffuser. These measurements show how flow heterogeneities are generated in the compressor and how they decay in the vaneless diffuser.

AeroMEMS polyimide based wall double hot-wire sensors for flow separation detection

2008 ◽  
Vol 142 (1) ◽  
pp. 130-137 ◽  
Author(s):  
Ulrich Buder ◽  
Ralf Petz ◽  
Moritz Kittel ◽  
Wolfgang Nitsche ◽  
Ernst Obermeier
Keyword(s):  
Flow Separation ◽  
Hot Wire

Two Way Coupled Fields Multi-Physics Modeling Is Investigated as an Additional Approach to Address Fluid Elastic Instability

2021 ◽  
Author(s):  
Michael Breach
Keyword(s):  
Time Delay ◽  
Relative Phase ◽  
Phase Lag ◽  
Elastic Instability ◽  
Coupled Fields ◽  
Flow Perturbation ◽  
Future Paper ◽  
Out Of Plane ◽  
Physics Modeling ◽  
Additional Approach

Abstract Two way coupled fields multi-physics modeling is investigated as an additional approach to address out-of-plane FEI. It is established in the literature that to model the damping-controlled fluid elastic instability, a finite time delay between tube vibration and fluid perturbation must be realized. The phase lag between tube vibration and flow perturbation due to damping must be adequately captured by the model. The effects of tube frequency, turbulence level, location, and mean gap velocity on the relative phase values must also be captured. This approach will allow the time delay between tube vibration and flow perturbation due to damping, as well as turbulence, and stiffness to be intrinsically modeled. We will introduce the applicability of the method to in-plane FEI in a future paper once we have based lined it against out of plane FEI empirical results.

Steam Plant Piping Vibration Study and Resolution

2007 ◽  
Author(s):  
Gregory Zysk ◽  
John Giamarino
Keyword(s):  
Flow Control ◽  
Distribution System ◽  
Dynamic Pressure ◽  
Control Valve ◽  
Piping System ◽  
Flow Control Valve ◽  
Flow Induced Vibration ◽  
Pressure Transducers ◽  
Equipment Operation ◽  
Generation Plant

The world’s largest district steam co-generation plant was successfully brought on line following major modifications in the spring of 2005. During the initial “shake-down” operation of the high pressure steam send-out system, piping vibrations were experienced, which disrupted flow meters and other equipment. Operation of one of five identical flow control valves, used in parallel to regulate steam flow to the street distribution system, resulted in the high vibration levels. To investigate the cause of the vibrations, a project was undertaken, which included testing of the piping system utilizing dynamic pressure transducers and accelerometers and engineering analysis of the acoustics and piping structural dynamics. Multiple combinations of open and closed valves were investigated, and the likely root cause was identified as flow-induced vibration originating at a tee in the system. A piping layout modification was designed. The modification consisted of rerouting the piping downstream of one flow control valve to bypass the source of the flow-induced vibration. Following the piping modification, further tests were conducted that showed the reconfiguration successfully mitigated the vibration.

Analysis of Unsteady Confined Viscous Flows With Variable Inflow Velocity and Oscillating Walls

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Dan Mateescu ◽  
Manuel Muñoz ◽  
Olivier Scholz
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Oscillation Frequency ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Viscous Flows ◽  
Staggered Grid ◽  
Engineering Systems ◽  
Flow Induced Vibration ◽  
Inflow Velocity

The inflow velocities in various components of many engineering systems often display variations in time (fluctuations) during the operation cycle, which may substantially affect the flow-induced vibrations and instabilities of these systems. For this reason, the aeroelasticity study of these systems should include the effect of the inflow velocity variations, which until now has not been taken into account. This paper presents a fluid-dynamic analysis of the unsteady confined viscous flows generated by the variations in time of the inflow velocities and by oscillating walls, which is required for the study of flow-induced vibration and instability of various engineering systems. The time-accurate solutions of the Navier–Stokes equations for these unsteady flows are obtained with a finite-difference method using artificial compressibility on a stretched staggered grid, which is a second-order method in space and time. A special decoupling procedure, based on the utilization of the continuity equation, is used in conjunction with a factored alternate direction scheme to substantially enhance the computational efficiency of the method by reducing the problem to the solution of scalar tridiagonal systems of equations. This method is applied to obtain solutions for the benchmark unsteady confined flow past a downstream-facing step, generated by harmonic variations in time of the inflow velocity and by an oscillating wall, which display multiple flow separation regions on the upper and lower walls. The influence of the Reynolds number and of the oscillation frequency and the amplitudes of the inflow velocity and oscillating wall on the formation of the flow separation regions are thoroughly analyzed in this paper. It was found that for certain values of the Reynolds number and oscillation frequency and amplitudes, the flow separation at the upper wall is present only during a portion of the oscillatory cycle and disappears for the rest of the cycle, and that for other values of these parameters secondary flow separations may also be formed.

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