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.

Applicability of the Wavy-Wall Model of Fluidelastic Instability to a Normal Triangular Tube Array

2008 ◽  
Author(s):  
Julie Harel ◽  
Craig Meskell
Keyword(s):  
Experimental Data ◽  
Triangular Array ◽  
Phase Lag ◽  
Pressure Perturbation ◽  
Wavy Wall ◽  
Decay Function ◽  
Wall Model ◽  
Line Array ◽  
Tube Arrays ◽  
Fluidelastic Instability

The Yetisir and Weaver formulation of the Lever and Weaver “wavy-wall” model for fluidelastic instability in tube arrays has been implemented for both normal triangular and in-line square arrays. The sensitivity of this model to the input parameters (i.e. attachment and separation points, decay function and phase lag function) has been examined. It was found that variations in the decay function were most significant and that the model behaved similarly for both array types. The predicted surface pressure perturbation due to tube displacement has then been compared with experimental data. For the in-line array the model behaviour compared well, while for the normal triangular array, the predictions were not representative of the experimental data. It is concluded that while the Yetisir and Weaver model can be applied successfully to in-line square arrays, it is not appropriate for densely packed normal triangular arrays.

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.

Characteristics of Fluidelastic Instability of Tube Rows in Crossflow

1988 ◽  
Vol 110 (1) ◽  
pp. 1-5
Author(s):  
S. S. Chen ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Diameter Ratio ◽  
Critical Flow ◽  
Jump Phenomenon ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Flow Velocities

An experimental study is reported that investigated the jump phenomenon in critical flow velocities for tube rows with different pitch-to-diameter ratios, and the excited and intrinsic instabilities for a tube row with a pitch-to-diameter ratio of 1.75. The experimental data provide additional insights into the instability phenomena of tube arrays in crossflow.

scholarly journals The Effect of Fins on Fluidelastic Instability in In-Line and Rotated Square Tube Arrays

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Robert H. Lumsden ◽  
David S. Weaver
Keyword(s):  
Finned Tube ◽  
Experimental Program ◽  
Effective Diameter ◽  
Process Industries ◽  
Finned Tubes ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
The Stability ◽  
Tube Pitch ◽  
Bare Tube

An experimental program was conducted to examine fluidelastic instability in in-line and rotated square finned tube arrays. Three arrays of each geometry type were studied: two with serrated, helically wound finned tubes of different fin densities and the third is a bare tube, which had the same base diameter as the finned tubes. The finned tubes under consideration were commercial finned tubes of a type typically used in the fossil and process industries. The addition of fins to tubes in heat exchangers enhances heat transfer due to the increased surface area and the turbulence produced by the flow moving over the fins. The resulting flow pattern/distribution due to the fins is, therefore, more complex than in bare tube arrays. Previous research has shown that an effective diameter of a finned tube is useful in the prediction of vortex shedding. This concept is used to compare the finned tube results with the existing bare tube array guidelines for fluidelastic instability. All of the tube arrays in the present study have the same tube pitch and have been scaled to have the same mass ratio. The results for rotated square arrays suggest that the use of an effective diameter is beneficial in the scaling of fluidelastic instability and the finned tube results are found to fit within the scatter of the existing data for fluidelastic instability. For in-line square arrays, the results indicate that fins significantly increase the stability threshold. An earlier version of this paper appeared at the ASME 2007 PVP Division Conference, PVP2007-26597.

Pitch and Pattern Effects on Streamwise Fluidelastic Instability in Tube Arrays

2019 ◽  
Author(s):  
Marwan Hassan ◽  
David Weaver
Keyword(s):  
Los Angeles ◽  
Channel Model ◽  
High Mass ◽  
Flow Induced Vibration ◽  
Geometric Patterns ◽  
Small Pitch ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
The Stability

Abstract Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.

On the Underlying Fluid Mechanics Responsible for Damping Controlled Fluidelastic Instability in Tube Arrays

2005 ◽  
Author(s):  
Craig Meskell
Keyword(s):  
Experimental Data ◽  
Current Model ◽  
Memory Function ◽  
Vortex Sheet ◽  
Transient Nature ◽  
Damping Parameter ◽  
Fluidelastic Instability ◽  
Static Fluid ◽  
Wake Model ◽  
Vorticity Transport

Granger and Paidoussis hypothesized that damping controlled fluidelastic instability is in fact due to the generation and convection of vorticity. In this paper a simple wake model consisting of a convecting vortex sheet is proposed to represent the transient nature of fluidelastic forces present in a tube array. Using this model, the memory function proposed by Granger and Paidoussis has been obtained by numerical integration without the need to calibrate the model with experimental data. The resulting function is found to compare well with the first and second order approximations which were determined empirically. However, the current model does not exhibit the physically unrealistic features of the approximations. Furthermore, the memory function has been combined with experimental data for the static fluid force to produce a prediction of the critical velocity for a range of mass damping parameter. This stability threshold is in reasonable agreement with experimental data. Therefore it is concluded that vorticity transport is in fact the mechanism responsible for damping controlled fluidelastic instability.

Towards a Validation Database for Simulation of Fluidelastic Instability in Normal Triangular Heat Exchanger Tube Arrays

2008 ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Surface Pressure ◽  
Cross Flow ◽  
Initial Step ◽  
Pressure Measurements ◽  
Dynamic Head ◽  
Flow Surface ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Large Asymmetry ◽  
Pitch Ratio

Models for fluidelastic instability are usually validated by comparing critical velocity predictions with experimental data. However, the scatter in this data make detailed validation problematic. As an initial step towards providing a validation database for fluidelastic instability, surface pressure measurements are presented for a cylinder in the third row of three normal triangular tube arrays (P/d = 1.32; 1.58; 1.97) with air cross flow. Surface pressure measurements were also made when the cylinder was statically displaced. Forces were calculated from the pressure measurements enabling an understanding of the force generation mechanism. The results show that the fluid force coefficients do not scale with the dynamic head but exhibit a dependency on Reynolds number and pitch ratio. However, no simple parametrisation was found for the lift force. Jet switching was found in P/d = 1.58 even when the tube was displaced. This phenomenon resulted in the large asymmetry observed in the pressure distribution around a static cylinder.

The Effects of Tube Array Geometry on Fluidelastic Instability in Heat Exchanger Tube Arrays in Cross Flow

2017 ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Experimental Data ◽  
Research Effort ◽  
Cross Flow ◽  
Triangular Arrays ◽  
Small Pitch ◽  
Fluidelastic Instability ◽  
Significant Research ◽  
Current Design ◽  
Pitch Ratio ◽  
Array Geometry

The shut-down of the San Onofre Nuclear Generating Station (SONGS) has been attributed to damaging streamwise Fluidelastic Instability (FEI) of the steam generator tubes, a phenomenon which has traditionally been assumed not to occur. This has generated a significant research effort to better understand this phenomenon and to develop appropriate design criteria for its prevention. Most current design codes are based on Connors criterion for FEI which neglects both streamwise FEI and the effects of tube array pattern and pitch ratio. It is becoming clear that array geometry and pitch ratio are important determining factors in FEI, especially in the streamwise direction. This paper presents an extension of the theory of Lever and Weaver to consider arrays of flexible fluid-coupled tubes which are free to become unstable in both the transverse and streamwise directions. This simplified modelling approach has the advantages of being very tractable for numerical parametric studies and having no need for experimental data input. Previous research by the authors has shown that the predictions of this model agree very well with the available experiments for parallel triangular arrays for both transverse and streamwise FEI. In this paper, the results of such studies are presented for the both transverse and streamwise FEI for square inline and normal triangular arrays and compared with the authors’ previous results for parallel triangular arrays. It is shown that FEI is strongly influenced by array geometry, especially for small pitch ratio arrays operating at low values of the mass damping parameter. The results show good agreement with the available experimental data.

Pitch and Pattern Effects On Streamwise Fluidelastic Instability in Tube Arrays

2021 ◽  
Author(s):  
Marwan A. Hassan ◽  
David S. Weaver
Keyword(s):  
Los Angeles ◽  
Channel Model ◽  
High Mass ◽  
Flow Induced Vibration ◽  
Geometric Patterns ◽  
Small Pitch ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
The Stability

Abstract Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.

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