Fluidelastic instability study in a rotated triangular tube array subject to two-phase cross-flow. Part I: Fluid force measurements and time delay extraction

2014 ◽  
Vol 49 ◽  
pp. 1-15 ◽  
Author(s):  
T. Sawadogo ◽  
N. Mureithi
Keyword(s):  
Time Delay ◽  
Cross Flow ◽  
Force Measurements ◽  
Two Phase ◽  
Fluid Force ◽  
Fluidelastic Instability ◽  
Flow Part ◽  
Delay Extraction

Streamwise Fluidelastic Instability of Tube Arrays in Two-Phase Cross Flow

2014 ◽  
Author(s):  
Stephen Olala ◽  
Njuki W. Mureithi
Keyword(s):  
Nuclear Power ◽  
Single Phase ◽  
Cross Flow ◽  
Force Measurements ◽  
Two Phase Flows ◽  
Two Phase ◽  
Fluid Force ◽  
Void Fractions ◽  
Tube Arrays ◽  
Fluidelastic Instability

In-plane instability of tube arrays has not been a major concern to steam generator designers until recently following observations of streamwise tube failure in a nuclear power plant in U.S.A. However, modeling of fluidelastic instability in two-phase flows still remains a challenge. In the present work, detailed steady fluid force measurements for a kernel of an array of tubes in a rotated triangular tube array of P/D=1.5 subjected to air-water two-phase flows for a series of void fractions and a Reynolds number (based on the pitch velocity), Re = 7.2 × 104 has been conducted. The measured steady fluid force coefficients and their derivatives, with respect to streamwise static displacements of the central tube, are employed in the quasi-steady model [1, 2], originally developed for single phase flows, to analyze in-plane fluidelastic instability of multiple flexible arrays in two-phase flows. The results are consistent with dynamic stability tests [3].

A Quasi-Steady In-Plane Fluidelastic Instability Analysis of a Rotated Triangular Tube Array in Two-Phase Cross Flow

2018 ◽  
Author(s):  
Stephen Olala ◽  
Njuki Mureithi
Keyword(s):  
Time Delay ◽  
Degrees Of Freedom ◽  
Dynamic Test ◽  
Cross Flow ◽  
Two Phase ◽  
Unsteady Forces ◽  
Fluidelastic Instability ◽  
Fluid Coupling ◽  
Flexible Tubes ◽  
Experimental Effort

In-plane fluidelastic instability is a dynamic phenomenon requiring fluid coupling of at least two degrees-of-freedom, in this case, at least two flexible tubes. Due to the nature of the mechanism causing streamwise fluidelastic instability, a purely experimental or an unsteady determination would require intensive experimental effort. As a compromise between experimental effort and prediction accuracy, the quasi-steady model is used in the current study. In the present work, previously measured quasi-steady and unsteady forces are used to estimate the time delay first between the displacement of an oscillating tube and the forces generated on itself then the time delay between the displacement of a central oscillating tube and the forces induced on the adjacent tubes. The estimated time delays are then used together with drag coefficients and derivatives to predict the in-plane fluidelastic instability in a rotated triangular tube array of P/D = 1.5 subjected to two-phase flow. The results closely replicate dynamic test results and confirm the predominance of the stiffness controlled mechanism and the potential of the quasi-steady model in accurately predicting streamwise fluidelastic instability in arrays subjected to two-phase flows.

Time Domain Models for Damping-Controlled Fluidelastic Instability Forces in Tubes With Loose Supports

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Marwan Hassan ◽  
Achraf Hossen
Keyword(s):  
Time Domain ◽  
Cross Flow ◽  
Work Rate ◽  
Interaction Parameters ◽  
Similar Response ◽  
Fluid Force ◽  
Support Interaction ◽  
Fluidelastic Instability ◽  
The Impact ◽  
Normal Work

This paper presents simulations of a loosely supported cantilever tube subjected to turbulence and fluidelastic instability forces. Several time domain fluid force models are presented to simulate the damping-controlled fluidelastic instability mechanism in tube arrays. These models include a negative damping model based on the Connors equation, fluid force coefficient-based models (Chen, 1983, “Instability Mechanisms and Stability Criteria of a Group of Cylinders Subjected to Cross-Flow. Part 1: Theory,” Trans. ASME, J. Vib., Acoust., Stress, Reliab. Des., 105, pp. 51–58; Tanaka and Takahara, 1981, “Fluid Elastic Vibration of Tube Array in Cross Flow,” J. Sound Vib., 77, pp. 19–37), and two semi-analytical models (Price and Païdoussis, 1984, “An Improved Mathematical Model for the Stability of Cylinder Rows Subjected to Cross-Flow,” J. Sound Vib., 97(4), pp. 615–640; Lever and Weaver, 1982, “A Theoretical Model for the Fluidelastic Instability in Heat Exchanger Tube Bundles,” ASME J. Pressure Vessel Technol., 104, pp. 104–147). Time domain modeling and implementation challenges for each of these theories were discussed. For each model, the flow velocity and the support clearance were varied. Special attention was paid to the tube/support interaction parameters that affect wear, such as impact forces and normal work rate. As the prediction of the linear threshold varies depending on the model utilized, the nonlinear response also differs. The investigated models exhibit similar response characteristics for the lift response. The greatest differences were seen in the prediction of the drag response, the impact force level, and the normal work rate. Simulation results show that the Connors-based model consistently underestimates the response and the tube/support interaction parameters for the loose support case.

scholarly journals On Damping and Fluidelastic Instability in a Tube Bundle Subjected to Two-Phase Cross-Flow

2007 ◽  
Author(s):  
Joaquin E. Moran ◽  
David S. Weaver
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Tube Bundle ◽  
Damping Ratio ◽  
Pressure Fluctuations ◽  
Cross Flow ◽  
Phase Changes ◽  
Working Fluid ◽  
Two Phase ◽  
Fluidelastic Instability

An experimental study was conducted to investigate damping and fluidelastic instability in tube arrays subjected to two-phase cross-flow. The purpose of this research was to improve our understanding of these phenomena and how they are affected by void fraction and flow regime. The working fluid used was Freon 11, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The damping measurements were obtained by “plucking” the monitored tube from outside the test section using electromagnets. An exponential function was fitted to the tube decay trace, producing consistent damping measurements and minimizing the effect of frequency shifting due to fluid added mass fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the Homogeneous Equilibrium Model (HEM) in terms of density and velocity predictions. It was found that the Capillary number, when combined with the two-phase damping ratio (interfacial damping), shows a well defined behaviour depending on the flow regime. This observation can be used to develop a better methodology to normalize damping results. The fluidelastic results agree with previously presented data when analyzed using the HEM and the half-power bandwidth method. The interfacial velocity is suggested for fluidelastic studies due to its capability for collapsing the fluidelastic data. The interfacial damping was introduced as a tool to include the effects of flow regime into the stability maps.

Estimation of the Time Delay Associated With Damping Controlled Fluidelastic Instability in a Normal Triangular Tube Array

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Time Delay ◽  
Cross Flow ◽  
Fluid Forces ◽  
Fluidelastic Instability ◽  
Order Of Magnitude ◽  
Sample Frequency ◽  
Pitch Ratio ◽  
Parameterized Model ◽  
Semi Empirical ◽  
Insight Into

Fluidelastic instability (FEI) produces large amplitude self-excited vibrations close to the natural frequency of the structure. For fluidelastic instability caused by the damping controlled mechanism, there is a time delay between tube motion and the resulting fluid forces but magnitude and physical cause of this is unclear. This study measures the time delay between tube motion and the resulting fluid forces in a normal triangular tube array with a pitch ratio of 1.32 subject to air cross-flow. The instrumented cylinder was forced to oscillate in the lift direction at three excitation frequencies for a range of flow velocities. Unsteady surface pressures were monitored with a sample frequency of 2 kHz at the mid plane of the instrumented cylinder. The instantaneous fluid forces were obtained by integrating the surface pressure data. A time delay between the tube motion and resulting fluid forces was obtained. The nondimensionalized time delay was of the same order of magnitude assumed in the semi-empirical quasi-steady model (i.e., τ2 = 0.29 d/U). Although, further work is required to provide a parameterized model of the time delay which can be embedded in a model of damping controlled fluidelastic forces, the data already provides some insight into the physical mechanism responsible.

Detailed flow and force measurements in a rotated triangular tube bundle subjected to two-phase cross-flow

2005 ◽  
Vol 20 (4) ◽  
pp. 567-575 ◽  
Author(s):  
M.J. Pettigrew ◽  
C. Zhang ◽  
N.W. Mureithi ◽  
D. Pamfil
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Force Measurements ◽  
Two Phase

DYNAMICS OF AN IN-LINE TUBE ARRAY SUBJECTED TO STEAM–WATER CROSS-FLOW. PART I: TWO-PHASE DAMPING AND ADDED MASS

2002 ◽  
Vol 16 (2) ◽  
pp. 123-136 ◽  
Author(s):  
T. NAKAMURA ◽  
K. HIROTA ◽  
Y. WATANABE ◽  
N.W. MUREITHI ◽  
T. KUSAKABE ◽  
...  
Keyword(s):  
Cross Flow ◽  
Added Mass ◽  
Two Phase ◽  
Phase Damping ◽  
Flow Part
Sign in / Sign up

Export Citation Format

Share Document