Numerical Estimation of Fluidelastic Instability in Staggered Tube Arrays

2009 ◽  
Author(s):  
H. Omar ◽  
M. Hassan ◽  
A. Gerber
Keyword(s):  
Moving Boundary ◽  
Tube Bundle ◽  
Navier Stokes ◽  
Numerical Estimation ◽  
Arbitrary Lagrangian Eulerian ◽  
Fluid Forces ◽  
Damping Parameter ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Reynolds Average

This study investigates the unsteady flow and the resulting fluidelastic forces in a tube bundle. Numerical simulations are presented for normal triangle tube arrays with pitch-to-diameter (P/d) ratios of 1.35, 1.75, and 2.5 utilizing a 2-dimensional model. In this model a single tube was forced to oscillate within an otherwise rigid array. Fluid forces acting on the oscillating tube and the surrounding tubes were estimated. The predicted forces were utilized to calculate fluid force coefficients for all tubes. The numerical model solves the Reynolds-Average Navier-Stokes (RANS) equations for unsteady turbulent flow, and is cast in an Arbitrary Lagrangian-Eulerian (ALE) form to handle mesh the motion associated with a moving boundary. The fluidelastic instability (FEI) was predicted for both single and fully flexible tube arrays over a mass damping parameter (MDP) range of 0.1 to 200. The effect of the P/d ratio and the Reynolds number on the FEI threshold was investigated in this work.

Numerical Estimation of Fluidelastic Instability in Tube Arrays

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Marwan Hassan ◽  
Andrew Gerber ◽  
Hossin Omar
Keyword(s):  
Unsteady Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
Fluid Forces ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Viable Approach ◽  
The Stability

This study investigates unsteady flow in tube bundles and fluid forces, which can lead to large tube vibration amplitudes, in particular, amplitudes associated with fluidelastic instability (FEI). The fluidelastic forces are approximated by the coupling of the unsteady flow model (UFM) with computational fluid dynamics (CFD). The CFD model employed solves the Reynolds averaged Navier–Stokes equations for unsteady turbulent flow and is cast in an arbitrary Lagrangian–Eulerian form to handle any motion associated with tubes. The CFD solution provides time domain forces that are used to calculate added damping and stiffness coefficients employed with the UFM. The investigation demonstrates that the UFM utilized in conjunction with CFD is a viable approach for calculating the stability map for a given tube array. The FEI was predicted for in-line square and normal triangle tube arrays over a mass damping parameter range of 0.1– 100. The effect of the P/d ratio and the Reynolds number on the FEI threshold was also investigated.

Numerical Characterization of the Area Perturbation and Timelag for a Vibrating Tube Subjected to Cross-Flow

2014 ◽  
Author(s):  
Salim El Bouzidi ◽  
Marwan Hassan ◽  
Lais L. Fernandes ◽  
Atef Mohany
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Theoretical Models ◽  
Design Guidelines ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Dynamic Simulations ◽  
Numerical Characterization ◽  
Fluidelastic Instability ◽  
The Impact

Fluidelastic instability can have disastrous effects on the integrity of steam generators. Over the last five decades there has been a great deal of research done in an attempt to understand this phenomenon. These efforts have resulted in several theoretical models and design guidelines. The semi-analytical model of fluidelastic instability initially developed by Lever and Weaver is based on a single tube in a channel flow. The mechanism responsible for instability was found to be one of flow redistribution. While previous studies have been able to characterize the pressure and velocity within a tube bundle, the behaviour of the area of the channel has not yet been fully investigated. The current study aims to characterize the area of the channel surrounding the tube. Reynolds Averaged Navier Stokes (RANS) equations are cast in an Arbitrary Lagrangian Eulerian (ALE) form and are used to compute the flow conditions in a rigid tube bundle due to a single flexible tube vibrating in the transverse direction. The properties of the velocity field are used to determine the channel boundaries. Properties of the channel area such as area perturbation, mean area, and area phase are investigated for various reduced flow velocities. Dynamic simulations are conducted to determine the impact on the stability threshold for transverse fluid force cases using a mass damping parameter range of 10–200.

Motion-Dependent Fluid Force Coefficients for Tube Arrays in Crossflow

2001 ◽  
Vol 123 (4) ◽  
pp. 429-436 ◽  
Author(s):  
S. S. Chen ◽  
G. S. Srikantiah
Keyword(s):  
Excitation Amplitude ◽  
Steam Generators ◽  
Fluid Force ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Stiffness Coefficients ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Fluid Damping ◽  
Series Of Experiments

Fluidelastic instability of tube arrays in crossflow is interesting academically and important in steam generators and heat exchangers. The key elements necessary to accurately predict fluidelastic instability of tube arrays in crossflow are motion-dependent fluid force coefficients. This paper presents several series of experiments that measure motion-dependent fluid forces for various tube arrays. Fluid damping and stiffness coefficients based on the unsteady flow theory were obtained as a function of reduced flow velocity, excitation amplitude, and Reynolds number, and the characteristics of motion-dependent fluid force coefficients were applied to provide some additional insights into fluidelastic instability.

Numerical Simulation of Cross-Flow-Induced Fluidelastic Vibration of Tube Arrays and Comparison With Experimental Results

1995 ◽  
Vol 117 (1) ◽  
pp. 31-39 ◽  
Author(s):  
F. L. Eisinger ◽  
M. S. M. Rao ◽  
D. A. Steininger ◽  
K. H. Haslinger
Keyword(s):  
Tube Bundle ◽  
Experimental Testing ◽  
Nonlinear Modeling ◽  
Cross Flow ◽  
Published Data ◽  
Nonlinear Structure ◽  
Numerical Studies ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Good Agreement

Tube arrays exposed to air, gas or liquid cross-flow can vibrate due to vortex-shedding, turbulence, or fluidelastic instability. The major emphasis of this paper is on the phenomenon of fluidelastic instability (or fluidelastic vibration). A numerical model is applied to the simulation of fluidelastic vibration of representative tubes in a tube bundle, based on S. S. Chen’s unsteady flow theory. The results are validated against published data based on linear cases. The model is then applied to a nonlinear structure of a U-bend tube bundle with clearances at supports, and the computed results compared to those obtained by experimental testing. The numerical studies were performed using the ABAQUS-EPGEN finite element code using a special subroutine incorporating fluidelastic forces. It is shown that the results of both the linear and nonlinear modeling are in good agreement with experimental data.

In-Plane Fluidelastic Instability Evaluation of Triangular Array Tube Bundle Using Fluid Force Measured Under Steam–Water Two-Phase Flow Condition

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Shingo Nishida ◽  
Seinosuke Azuma ◽  
Hideyuki Morita ◽  
Kazuo Hirota ◽  
Ryoichi Kawakami ◽  
...  
Keyword(s):  
Critical Velocity ◽  
Tube Bundle ◽  
Straight Tube ◽  
Two Phase ◽  
Fluid Force ◽  
Stability Analyses ◽  
Fluid Forces ◽  
Fluidelastic Instability ◽  
The Difference ◽  
Unsteady Fluid

Abstract Recently, tube-to-tube wear indications of triangular tube bundle steam generators (SGs) caused by fluidelastic instability (FEI) in the in-plane direction of U-bend region (in-plane FEI) have been reported. Several experiments were conducted to investigate the characteristics of in-plane FEI by our research groups. In a series of experiments, particular characteristics of in-plane FEI were found. For example, there are the critical velocity difference between the in-plane and the out-of-plane directions, the difference between straight tube bundle tests and U-bend tube bundle tests, etc. To explain these characteristics, unsteady fluid force acting on tubes were measured. The experimental investigation was conducted under high temperature and high-pressure steam–water flow conditions close to the SGs. Stability analyses were conducted using the measured unsteady fluid forces as inputs. First, stability analyses were done to simulate straight tube bundle tests. Analysis results agreed well with experiments and it could explain the effect on critical velocity trend by number of flexible tubes and directions of vibration. Second, U-tube stability analyses were performed by applying unsteady fluid force coefficients for each location of U-bend tube finite element method (FEM) model. From the results, mechanisms of in-plane FEI were understood.

The Effect of Streamwise Tube Motion on the Unsteady Fluid Forces in a Normal Triangle Tube Array

2015 ◽  
Author(s):  
Salim El Bouzidi ◽  
Marwan Hassan
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Arbitrary Lagrangian Eulerian ◽  
Streamwise Direction ◽  
Navier Stokes Equations ◽  
Critical Flow Velocity ◽  
Flow Perturbation ◽  
Short Period ◽  
Fluidelastic Instability

Fluidelastic instability is generally regarded as the most severe type of flow excitation mechanism. When this mechanism prevails, it could cause serious damage to tube arrays in a very short period of time. This mechanism is characterized by a critical flow velocity beyond which the tubes undergo unstable oscillations. Recently, a number of experimental investigations showed that it is possible to have instability in the streamwise direction; previously, it was believed that fluidelastic instability was only a concern in the direction transverse to the flow. The purpose of this study is to characterize the flow in the channels surrounding a vibrating tube in a normal triangular bundle with P/d = 1.5. The tube is oscillating in the streamwise direction with a constant amplitude. Numerical simulations were conducted by solving the unsteady Reynolds Averaged Navier-Stokes equations (uRANS) cast in Arbitrary Lagrangian-Eulerian (ALE) form. The unsteady flow perturbation is estimated along the flow channel. The pressure perturbation is used to compute the streamwise unsteady force coefficients in the context of Chen’s model. The perturbation phase and decay are extracted and utilized in the framework of the Lever & Weaver model to study the stability of tube bundles due to tube motion in the streamwise direction.

Numerical Analysis of Fluidelastic Instability in a Normal Triangular Tube Array

2009 ◽  
Author(s):  
Stephen Gillen ◽  
Craig Meskell
Keyword(s):  
Tube Bundle ◽  
Pressure Coefficient ◽  
Navier Stokes ◽  
Force Coefficients ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
Flow Through ◽  
Critical Velocities ◽  
Experimental Values ◽  
Reynolds Number Dependence

Investigation of steady flow through a normal triangular tube bundle is carried out numerically using a 2D Reynolds Averaged Navier-Stokes solver. Pitch to diameter ratios of 1.25 and 1.32 are simulated with a single tube displaced and the resulting force coefficients measured. Comparison of pressure coefficient with experimental data indicates simulations provide a reliable indication of Reynolds number dependence. These fluid force coefficients are then used as input into the quasi-unsteady model in order to predict the critical velocity of damping controlled fluidelastic instability for a single degree of freedom tube within an array. The predicted critical velocities are in the range of empirical data from the literature. The predicted critical velocities for the pitch ratio of 1.25 are within 30% of the experimental values previously reported.

Computation of Velocity Profiles and Pressure Coefficients for a Laminar Flow of Air Over Staggered Array of Tubes

2005 ◽  
Author(s):  
Ramin Rahmani ◽  
Ahad Ramezanpour ◽  
Iraj Mirzaee ◽  
Hassan Shirvani
Keyword(s):  
Laminar Flow ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Tube Arrays ◽  
Volume Method

In this study a two dimensional, steady state and incompressible laminar flow for staggered tube arrays in crossflow is investigated numerically. A finite-volume method is used to discretize and solve the governing Navier-Stokes equations for the geometries expressed by a boundary-fitted coordinate system. Solutions for Reynolds numbers of 100, 300, and 500 are obtained for a tube bundle with 10 longitudinal rows. Local velocity profiles on top of each tube and corresponding pressure coefficient are presented at nominal pitch-to-diameter ratios of 1.33, 1.60, and 2.00 for ES, ET, and RS arrangements. Differences in location of separation points are compared for three different arrangements. The predicted results on flow field for pressure coefficient showed a good agreement with available experimental measurements.

Fluid Damping and Fluid Stiffness of a Tube Row in Crossflow

1994 ◽  
Vol 116 (4) ◽  
pp. 370-383 ◽  
Author(s):  
S. S. Chen ◽  
S. Zhu ◽  
J. A. Jendrzejczyk
Keyword(s):  
Flow Velocity ◽  
Water Channel ◽  
Excitation Frequency ◽  
Excitation Amplitude ◽  
Design Guideline ◽  
Fluid Forces ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Fluid Damping ◽  
Reliable Design

Motion-dependent fluid forces acting on a tube array were measured as a function of excitation frequency, excitation amplitude, and flow velocity. Fluid-damping and fluid-stiffness coefficients were obtained from measured motion-dependent fluid forces as a function of reduced flow velocity and excitation amplitude. The water channel and test setup provide a sound facility for obtaining key coefficients for fluidelastic instability of tube arrays in crossflow. Once the motion-dependent fluid-force coefficients have been measured, a reliable design guideline, based on the unsteady flow theory, can be developed for fluidelastic instability of tube arrays in crossflow.

Pitch and Mass Ratio Effects on Transverse and Streamwise Fluidelastic Instability in Parallel Triangular Tube Arrays

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Marwan Hassan ◽  
David Weaver
Keyword(s):  
Experimental Data ◽  
Relative Importance ◽  
Mass Ratio ◽  
Damping Parameter ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
Fluid Coupling ◽  
Lift And Drag ◽  
Tube Pitch

The simple tube and channel theoretical model for fluidelastic instability (FEI) in tube arrays, as developed by Hassan and Weaver, has been used to study the effects of pitch ratio and mass ratio on the critical velocity of parallel triangular tube arrays. Simulations were carried out considering fluidelastic forces in the lift and drag directions independently and acting together for cases of a single flexible tube in a rigid array and a fully flexible kernel of seven tubes. No new empirical data were required using this model. The direction of FEI as well as the relative importance of fluid coupling of tubes was studied, including how these are affected by tube pitch ratio and mass ratio. The simulation predictions agree reasonably well with available experimental data. It was found that parallel triangular tube arrays are more vulnerable to streamwise FEI when the pitch ratio is small and the mass-damping parameter (MDP) is large.

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