Steam Generator Tube Vibrations: Experimental Determination Versus ALE Computation of Fluidelastic Forces

2003 ◽  
Author(s):  
Z. Bendjeddou ◽  
E. Longatte ◽  
A. Adobes ◽  
M. Souli
Keyword(s):  
Experimental Determination ◽  
Moving Boundary ◽  
Reynolds Numbers ◽  
High Amplitude ◽  
Industrial Applications ◽  
Critical Flow Velocity ◽  
Tube Arrays ◽  
Elastic Forces ◽  
Tube Bundles ◽  
High Reynolds

In heat exchanger tube bundles like in many others industrial applications, fluid structure interaction is a crucial problem to overcome. Flow-induced tube vibration in tube bundles is due to two main kinds of physical effects: (1) fluid-elastic forces caused by structure motion; (2) turbulent forces due to vortex generation at high Reynolds numbers. The second component, turbulent excitation, is independent on structure motion and may generate wear and fatigue damage while the first component may lead to fluid-elastic instability inducing high amplitude displacement and possible tube short term failure. In this context many studies are carried out in order to develop methods for the identification of critical flow velocity in tube arrays. In the present work two methods are presented: (1) the first one relies on experimental measurements, it is fitted with analytical modeling and provides fluid-elastic coefficients; (2) the second one relies on numerical simulation using Computational Fluid Dynamics Codes (CFD) involving moving boundary techniques; it provides fluid force estimates and in some cases it makes it possible to simulate tube vibrations. The first part is devoted to experimental determination of fluid-elastic forces. A numerical method for prediction of fluid-elastic effects in fluid at rest is presented in the second section. Results of both methods are compared in the third part.

Convective micromixers — design and industrial applications

2008 ◽  
Vol 222 (5) ◽  
pp. 807-816 ◽  
Author(s):  
N Kockmann
Keyword(s):  
Transient Flow ◽  
Phase Particle ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Industrial Applications ◽  
Particle Generation ◽  
Vitamin E Acetate ◽  
Mass Flowrate ◽  
High Reynolds ◽  
20 Nm

Convective static micromixers operate with high Reynolds numbers ( Re from 100 to 1000) in relatively large microchannels (100–1000 μm) for high flowrates and low risk of fouling and blocking. Typical flow characteristics of symmetrical mixing in T-shaped micromixers are presented with transient flow for Re number larger than 240. The simulation results are assisted by experimental data. Parallel mixing elements increase the mass flowrate up to 25 kg/h with 100 kPa pressure loss. The typical flow characteristics are described, which are essential for successful mixing devices. Three dimensionless parameters are introduced to describe the mixing performance and effectiveness of such devices. Particle generation are critical in microchannels due to fouling issues. The gas phase particle generation from homogeneous condensation of vitamin E acetate is described, reaching to particle diameters of 20 nm from temporal temperature gradients of about 1.6×106 K/s. In liquid phase, the reactive precipitation of BaSO4 is investigated, leading to particle diameters below 100 nm.

Fluctuating Lift Forces of the Karman Vortex Streets on Single Circular Cylinders and in Tube Bundles: Part 3—Lift Forces in Tube Bundles

1972 ◽  
Vol 94 (2) ◽  
pp. 623-628 ◽  
Author(s):  
Y. N. Chen
Keyword(s):  
Second Harmonic ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Critical Flow Velocity ◽  
Pressure Drag ◽  
Tube Bundles ◽  
Karman Vortex ◽  
Lift Forces

The trend of the fluctuating lift coefficient CL and the dimensionless shedding frequency S (Strouhal number) of the vortex in tube bundles at higher Reynolds numbers R will be predicted by the course of the steady pressure drag coefficient CD at the corresponding R ranges. Furthermore, some measurements of the vortex lift forces in tube bundles will be given. It reveals that the lift force for certain small transverse tube spacings possesses a strong second harmonic. The tubes and, therefore, the transverse gas column in the tube bundle channel can be excited to vibrate in resonance either at the critical flow velocity or at its half value. Finally, the coupled vibration between the vortex shedding and the transverse gas column will be covered with some experiments.

Numerical Simulation of Tube Bundle Vibrations in Cross Flows

2002 ◽  
Author(s):  
E. Longatte ◽  
Z. Bendjeddou ◽  
M. Souli
Keyword(s):  
Numerical Simulation ◽  
Dynamic Behaviour ◽  
Tube Bundle ◽  
Numerical Estimate ◽  
Time History ◽  
Numerical Prediction ◽  
Critical Flow Velocity ◽  
Ale Formulation ◽  
Elastic Forces ◽  
Tube Bundles

In many industrial applications, mechanical structures like heat exchanger tube bundles are subjected to complex flows causing possible vibrations and damage. Part of fluid forces are coupled with tube motion and these so-called fluid-elastic forces can affect the structure dynamic behaviour generating possible instabilities and leading to short term failures through high amplitude vibrations. Most classical fluid force identification methods rely on structure response experimental measurements associated with convenient data processes. Owing to recent improvements in Computational Fluid Dynamics, numerical simulation of flow-induced vibrations is now practicable for industrial purposes. The present paper is devoted to the computation of fluid-elastic forces acting on tube bundles subjected to one-phase cross flows. What is the numerical process ? In the case where fluid-elastic effects are not significant and are restricted to added mass effects, there is no real coupling between structure and fluid motion. The structure displacement is not supposed to affect flow patterns. Thus it is possible to solve the fluid and the structure problems separately by using a fixed non-moving mesh for the fluid dynamic computation. Lift and drag forces acting on tube bundles can be computed numerically by using Large Eddy Simulation. Their spectrum and time history can be introduced as inlet conditions in the mechanical calculation providing the tube vibratory response. On the contrary when fluid-elastic effects can not be neglected, in presence tube bundles subjected to cross flows for example, a coupling between flow and structure computations is required. Such a calculation is performed in the present work. An improved numerical approach has been developed and applied to the fully numerical prediction of the dynamic behaviour of a flexible tube belonging to a fixed tube bundle subjected to cross flows. The purpose is to be able to provide a numerical estimate of the critical flow velocity for the threshold of fluidelastic instability of tube bundle without experimental investigation. The methodology consists in simulating in the same time thermohydraulics and mechanics problems by using an Arbitrary Euler Lagrange (ALE) formulation for the fluid computation. Numerical results turn out to be consistent with available experimental data obtained in the same configuration. This work is a first step in the numerical prediction of tube bundle vibrations in presence of cross flows.

A Linear Model for the Onset of Whistling in Corrugated Pipe Segments: Influence of Geometry

2013 ◽  
Author(s):  
Oleksii Rudenko ◽  
Dennis Meertens ◽  
Güneş Nakiboğlu ◽  
Avraham Hirschberg ◽  
Stefan Belfroid
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Industrial Applications ◽  
Small Scale ◽  
Composite Pipe ◽  
Pipe Segment ◽  
Flow Through ◽  
Smooth Pipe ◽  
High Reynolds ◽  
Semi Empirical

Corrugated pipes combine small-scale rigidity and large-scale flexibility, which makes them very useful in industrial applications. The flow through such a pipe can induce strong undesirable whistling noises and even drive dangerous structural vibrations. Placing a short corrugated segment along a smooth pipe reduces the whistling, while this composite pipe still retains some global flexibility. The whistling is reduced by thermo-viscous damping in the smooth pipe segment. A linear semi-empirical model is proposed that allows to predict the critical Mach numbers at the onset of whistling for a composite pipe at moderately high Reynolds numbers. Experimental results for corrugated pipes of three different corrugations geometries are presented revealing fair agreement with the theory. In addition, the model indicates that even for a corrugated pipe segment with an anechoic termination, corresponding to a very long smooth pipe segment, there exists a finite critical Mach number above which the whistling occurs.

TRANSONIC CROSS FLOW (M∞ = 0.8) OVER A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

2012 ◽  
Vol 43 (5) ◽  
pp. 589-613
Author(s):  
Vyacheslav Antonovich Bashkin ◽  
Ivan Vladimirovich Egorov ◽  
Ivan Valeryevich Ezhov ◽  
Sergey Vladimirovich Utyuzhnikov
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

Oscillatory control of separation at high Reynolds numbers

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 1062-1071 ◽  
Author(s):  
A. Seifert ◽  
L. G. Pack
Keyword(s):  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

Turbulent vortex breakdown at high Reynolds numbers

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 825-834
Author(s):  
F. Novak ◽  
T. Sarpkaya
Keyword(s):  
Vortex Breakdown ◽  
Reynolds Numbers ◽  
Turbulent Vortex ◽  
High Reynolds Numbers ◽  
High Reynolds

Drag Measurements on Long Thin Cylinders at Small Angles and High Reynolds Numbers

2004 ◽  
Author(s):  
William L. Keith ◽  
Kimberly M. Cipolla ◽  
David R. Hart ◽  
Deborah A. Furey
Keyword(s):  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Sign in / Sign up

Export Citation Format

Share Document