Phase Lag Model for Fluidelastic Instability in Square Cylinder Arrangement

2015 ◽  
Author(s):  
Mustapha Benaouicha ◽  
Elisabeth Longatte ◽  
Franck Baj
Keyword(s):  
Dynamic Instability ◽  
Fluid Velocity ◽  
Cross Flow ◽  
Theoretical Models ◽  
Phase Lag ◽  
Structure Parameters ◽  
Square Cylinder ◽  
Theoretical Formulation ◽  
Lag Model ◽  
Pitch Ratio

In this paper, a phase lag model is proposed in order to predict the fluid velocity threshold for fluidelastic dynamic instability of a square cylinder arrangement under cross flow. A theoretical formulation of a total damping, including the added damping in still fluid, the damping due to fluid flow and the damping derived from the phase shift between the fluid force and tube displacement, is given. A function of fluid and structure parameters, such as reduced velocity, pitch ratio and Scruton number, is thus obtained. It is shown that this function, taken as function of the reduced velocity variable, vanishes at the critical reduced velocity from which the fluidelastic dynamic instability of the tube occurs. Obviously, the value of the critical velocity is depending on other fluid-structure parameters. The obtained results are compared to experimental ones and those obtained from other theoretical models.

Stability of Cylinder Arrangement in Potential Flow

2013 ◽  
Author(s):  
M. Benaouicha ◽  
E. Longatte ◽  
F. Baj
Keyword(s):  
Dynamic Instability ◽  
Cross Flow ◽  
Physical Parameters ◽  
Square Cylinder ◽  
Flow Induced Vibration ◽  
Structure Interaction ◽  
Flow Parameters ◽  
Instability Development ◽  
Pitch Ratio ◽  
Solid Dynamics

Fluid-structure interaction and flow-induced vibration in square cylinder arrangement under incompressible, ideal and irrotational cross flow are investigated in the present paper. The purpose of this study is to contribute to better understanding of external fluid loads exerted on long thin cylinders inducing the flow perturbations. Indeed, in presence of high flow confinement, the thin cylinders could be subjected to strong vibrations, which may lead to instability development and therefore to a risk of break or collision. The dynamic instability of the mobile tube, according to some geometric and flow parameters such as reduced velocity and pitch ratio, is then studied. A semi-analytical approach is used to determine a stability criterion of the dynamical system. In addition, the influence of key physical parameters on fluid-solid dynamics interaction is quantified in the studied configuration.

Fluidelastic Vibration Analysis of Normal Square Finned Tube Arrays in Water Cross Flow

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Sandeep R. Desai ◽  
Aslam A. Maniyar
Keyword(s):  
Vortex Shedding ◽  
Fluid Velocity ◽  
Cross Flow ◽  
Finned Tube ◽  
Instability Threshold ◽  
Experimental Program ◽  
Triangular Arrays ◽  
Array Pattern ◽  
Tube Arrays ◽  
Pitch Ratio

An experimental program was carried out by subjecting normal square finned tube arrays to gradually increasing water cross flows. In all, total six tube arrays were tested—three having pitch ratio 2.1 and remaining three of pitch ratio 2.6. Under each category, three arrays tested were: plain array, coarse finned array, and fine finned array. The objective of the research was to determine the fluid velocity at which each of the six arrays becomes fluidelastically unstable. The experiments were started with tests on plain arrays to establish them as a datum case by comparing their test results with published results on plain arrays having lower pitch ratios. This was then followed by testing of finned arrays to study the effect of fins on the instability threshold. The tubes were subjected to a gradually increasing flow rate of water from 10 m3/h to the point where instability was reached. The results of the present work are compared with author's earlier published results for parallel triangular arrays in water. The research outcomes help to study the effect of pitch ratio, tube array pattern, and fin density on the instability threshold. The results show that instability is delayed due to the addition of the fins. It is also concluded that normal square arrays should be preferred over parallel triangular arrays to avoid fluidelastic vibrations. The vortex shedding behavior studied for all the arrays shows that small peaks before fluidelastic instability are due to vortex shedding.

The initial stress effect on a thermoelastic micro-elongated solid under the dual-phase-lag model

2021 ◽  
Vol 127 (9) ◽  
Author(s):  
Mohamed I. A. Othman ◽  
Sarhan Y. Atwa ◽  
Ebtesam E. M. Eraki ◽  
Mohamed F. Ismail
Keyword(s):  
Initial Stress ◽  
Stress Effect ◽  
Phase Lag ◽  
Dual Phase ◽  
Lag Model

Thermoelastic Bresse system with dual-phase-lag model

2021 ◽  
Vol 72 (3) ◽  
Author(s):  
Noelia Bazarra ◽  
Ivana Bochicchio ◽  
José R. Fernández ◽  
Maria Grazia Naso
Keyword(s):  
Phase Lag ◽  
Dual Phase ◽  
Bresse System ◽  
Lag Model

Cross-flow pressure measurement on a 2D square cylinder

2001 ◽  
Vol 89 (14-15) ◽  
pp. 1459-1470 ◽  
Author(s):  
Y.F. Li ◽  
P.J. Richards ◽  
R.G.J. Flay
Keyword(s):  
Pressure Measurement ◽  
Cross Flow ◽  
Square Cylinder ◽  
Flow Pressure

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.

Three-phase lag model of thermo-elastic interaction in a 2D porous material due to pulse heat flux

2020 ◽  
Vol 30 (12) ◽  
pp. 5191-5207 ◽  
Author(s):  
Aatef Hobiny ◽  
Faris S. Alzahrani ◽  
Ibrahim Abbas
Keyword(s):  
Volume Fraction ◽  
Elastic Interaction ◽  
Phase Lag ◽  
Thermoelastic Wave ◽  
Content Type ◽  
Three Phase ◽  
Stress Components ◽  
Eigen Values ◽  
Lag Model ◽  
The Difference

Purpose The purposes of this study, a generalized model for thermoelastic wave under three-phase lag (TPL) model is used to compute the increment of temperature, the components of displacement, the changes in volume fraction field and the stress components in a two-dimension porous medium. Design/methodology/approach By using Laplace-Fourier transformations with the eigen values methodologies, the analytical solutions of all physical variables are obtained. Findings The derived methods are estimated with numerical outcomes which are applied to the porous media in simplified geometry. Originality/value Finally, the outcomes are represented graphically to display the difference among the models of the TPL and the Green and Naghdi (GNIII) with and without energy dissipations.

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