Experiments on vertical slender flexible cylinders clamped at both ends and subjected to axial flow

Modarres‐Sadeghi, Yahya; Paı̈doussis, M.P.; Semler, C.; Grinevich, E.

doi:10.1098/rsta.2007.2131

Cited by 28 publications

(17 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This theory showed, just like the linear theory, the existence of a flutter motion. An additional series of experiments, performed by Modarres-Sadeghi et al (2008), was in qualitative agreement with the non-linear theory. However, there is a difference of 40% in the threshold at which flutter is predicted and the fluttering motion was also observed around the neutral axis and not around a buckled state, as calculated by weakly non-linear theory.…”

Section: Introductionsupporting

confidence: 55%

See 1 more Smart Citation

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

Ridder

Degroote

Tichelen

et al. 2017

Journal of Fluids and Structures

View full text Add to dashboard Cite

External fluid flow has a number of effects on the dynamics of a submersed structure: e.g., a solitary cylinder exposed to an external flow experiences added mass and damping due to the presence of the surrounding fluid. At high axial flow velocities relative to the stiffness of the cylinder, coupled instabilities such as flutter and divergence occur. Compared to a solitary cylinder, a cluster of cylinders also experiences inter-cylinder coupling: pressure perturbations in the fluid due to the movement or acceleration of one cylinder force another cylinder to move. Consequently, the different cylinders can move in organized patterns.In this contribution, modal characteristics of a 7-rod bundle will be predicted by linear theory as well as by coupled CFD-CSM (Computational Fluid Dynamics -Computational Structure Mechanics) calculations. In the first part, fluid forces which lead to coupling of motion are computed with classical potential flow theory and URANS (Unsteady Reynolds-Averaged Navier-Stokes). Those forces are divided in a contribution in phase with the acceleration and a contribution in phase with the velocity of a cylinder. In the second part, modal characteristics of a 7 cylinder bundle are computed with coupled CFD-CSM simulations. The initial perturbations, which are required for the time-domain simulations come from a simplified structural model, with potential flow coupling between cylinders. The results are compared to linear theory. In the final part, approximations are proposed to predict upper and lower bounds of eigenfrequencies and damping, using calculations with only one cylinder.

show abstract

Section: Introductionsupporting

confidence: 55%

“…At even higher flow velocity (not shown on the graph), the eigenfrequency goes to zero, and the cylinders will buckle. Note that a solitary cylinder behaves similarly (De Ridder et al, 2015;Modarres-Sadeghi et al, 2008).…”

Section: First Mode Groupmentioning

confidence: 99%

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

Ridder

Degroote

Tichelen

et al. 2017

Journal of Fluids and Structures

View full text Add to dashboard Cite

show abstract

“…In contrast to linear theory, it predicts a fluttering motion around a buckled state and not around the neutral axis. To verify the outcome of nonlinear theory, an additional series of experiments were performed by Modarres-Sadeghi et al (2008). The results of the experiments were in qualitative agreement with the nonlinear theory.…”

Section: Introductionsupporting

confidence: 48%

“…The method was however only applied for subcritical conditions. The goal of this contribution is to compute the dynamics in a broader range of flow velocities (including the unstable regime) of the clamped-clamped cylinder in turbulent axial flow of Modarres-Sadeghi et al (2008).…”

Section: Introductionmentioning

confidence: 99%

Simulating the fluid forces and fluid-elastic instabilities of a clamped–clamped cylinder in turbulent axial flow

Ridder

Doaré

Degroote

et al. 2015

Journal of Fluids and Structures

View full text Add to dashboard Cite

In this article, the fluid forces and the dynamics of a flexible clamped-clamped cylinder in turbulent axial flow are computed numerically. In the presented numerical model, there is no need to tune parameters for each specific case or to obtain coefficients from experiments. The results are compared with the dynamics measured in experiments available in literature. The specific case studied here consists of a silicone cylinder mounted in axial water flow. Computationally it is found that the cylinder loses stability first by buckling. The threshold for buckling is in quantitative agreement with experimental results and weakly-nonlinear theory. At higher flow speed a fluttering motion is predicted, in agreement with experimental results. It is also shown that even a small misalignment between the flow and the structure can have a significant impact on the dynamical behavior. To provide insight in the results of these fluid-structure interaction simulations, forces are computed on rigid inclined and curved cylinders, showing the existence of two different flow regimes. Furthermore it is shown that the inlet turbulence state has a non-negligible effect on these forces and thus on the dynamics of the cylinder.

show abstract

“…As both experimental and analytical capabilities advance, the critical research path in developing and implementing fluid-structure interaction models entails to (i) formulating generalized equations of motion, as a superset of the flow-oscillator models and (ii) developing experimentally derived, semi-analytical functions to describe key terms in the governing equations of motion. Modarres-Sadeghi et al (2008) discuss experiments on vertical slender flexible cylinders clamped at both ends and subjected to axial flow. Three series of experiments were conducted in order to observe the dynamical behaviour of the system, and the results are compared with theoretical predictions.…”

mentioning

confidence: 99%

Introduction. Experimental nonlinear dynamics of fluids

Wiercigroch

2007

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Nearly six decades ago, Stoker, in the introduction to his seminal book on nonlinear vibrations (Stoker 1950), pointed out 'It is perhaps worth while to consider for a moment the reasons why one should be interested particularly in the nonlinear problems in mechanics. Basically the reason is, of course, that all of the problems in mechanics are nonlinear from the outset, and the linearizations commonly practiced are an approximating device which is often a confession of defeat in the challenge presented by nonlinear problems as such'. This powerful statement is echoed in the celebrated book on nonlinear oscillators (Andronov et al. 1966), which provides a very comprehensive source of the theoretical foundations and applications in the area of nonlinear oscillations. The concepts of slow and fast oscillations, small and large terms in solutions, and periodicity have been clearly introduced in this book by solving various dynamical problems. In more recent works (e.g. Guckenheimer & Holmes 1983;Thompson & Stewart 1986), one can find a systematic approach to model and analyse nonlinear systems exhibiting chaos.Since the invention of digital computers, the interest in the area of nonlinear mechanics, and nonlinear dynamics in particular, has grown nearly in an exponential manner. Currently we have in excess of 40 journals that publish nonlinear dynamics results. However, there is a huge disproportion between numbers of theoretical and experimental papers. A very conservative estimate would account for approximately 5% of experimental articles. Experiments are vital to confirm new theories, make viable predictions and ultimately to establish firm foundations for developments in science and technology.The main aim of arranging and compiling this theme is to perhaps address in a small but powerful way the misbalance mentioned above. The theme comprising a total 12 papers has two issues 'Experimental nonlinear dynamics I. Solids' and 'Experimental nonlinear dynamics II. Fluids'.This second part of the theme is formed from five papers written by world experts in the areas of fluid-structure interactions and fluids. The first two articles by Benaroya & Gabbai (2008) and Modarres-Sadeghi et al. (2008) form a bridge between solids and fluids as they consider fluid-structure interactions. The following three contributions are focused on the nonlinear effects originating mainly from fluids.

show abstract

Experiments on vertical slender flexible cylinders clamped at both ends and subjected to axial flow

Cited by 28 publications

References 26 publications

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

Simulating the fluid forces and fluid-elastic instabilities of a clamped–clamped cylinder in turbulent axial flow

Introduction. Experimental nonlinear dynamics of fluids

Contact Info

Product

Resources

About