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Article: Fluid-Induced Vibration Frequency and Damping of a Coaxial Cylinder in a Quiescent Viscous Medium: Theoretical and Numerical Predictions.

Submitted by lagrangr on
research
Fluid Structure Interaction

This study, motivated by applications in nuclear engineering, examines the fluid-induced vibrations of a flexible inner cylinder concentrically positioned within a rigid outer cylinder, separated by a quiescent Newtonian viscous fluid. Building on our previous work, which focused on forced motions, we extend the theoretical formulation to account for vibrations induced by fluid forces. A new expression for the linear fluid force is derived, introducing a fluid transfer function that depends on key dimensionless numbers such as the aspect ratio, radius ratio, and Stokes number.

Article: Turbulence-induced vibration in annular flow of a rigid cylinder mounted on a cantilever beam

Submitted by lagrangr on
research
Fluid Structure Interaction
fluid-elastic instability

This study investigates the fluid–structure interaction of two coaxial cylinders separated by a Newtonian fluid under turbulent axial flow. The theoretical framework treats the inner cylinder as a rigid body mounted on a flexible blade modeled as a Rayleigh beam. The goals of this study are to determine the free vibration modes and frequencies, identify the fluid-elastic instability threshold, and establish an analytical expression for the mean-square displacement of the structure.

Article: A frequency-independent second-order framework for the formulation of experimental fluidelastic forces using hidden flow variables

Submitted by lagrangr on
research
Fluid Structure Interaction
Multiphase Flows
Elastic instability
steam generator tube

The importance of fluidelastic forces in flow-excited vibrations is crucial, in view of their damaging potential. Flow-coupling coefficients are often experimentally obtained from vibration experiments, performed within a limited experimental frequency range. For any given flow velocity, these coefficients are typically frequency-dependent, as amply documented in the literature since the seminal work of Tanaka and Takahara.

Article: A new criterion for the instability threshold of a square tube bundle subject to an air-water cross-flow

Submitted by lagrangr on
research
Fluid Structure Interaction
Multiphase Flows
Elastic instability
steam generator tube

We investigate the fluid-elastic instability of a square tube bundle subject to two-phase cross-flow. A dimensional analysis is carried out, leading to a new criterion of instability. This criterion establishes a direct link with the instability thresholds in single-phase flows. In parallel to the dimensional analysis, experimental work is carried out to i) determine the instability thresholds in single-phase flows (new relation between the Scruton, Stokes and Reynolds number), ii) to test the validity of the two-phase flow instability criterion, derived from the dimensional analysis.

Article: Interaction of two cylinders immersed in a viscous fluid. On the effect of moderate Keulegan–Carpenter numbers on the fluid forces

Submitted by lagrangr on
research
Fluid Structure Interaction

This work deals with the hydrodynamic interaction of two parallel circular cylinders, with identical radii, immersed in a viscous fluid initially at rest. One cylinder is stationary while the other one is imposed a harmonic motion with a moderate amplitude of vibration. The direction of motion is parallel to the line joining the centers of the two cylinders. The two dimensional fluid–structure problem is numerically solved by the Arbitrary Lagrangian–Eulerian method implemented in the open-source CFD code TrioCFD.

Article: Viscous Theory for the Vibrations of Coaxial Cylinders: Analytical Formulas for the Fluid Forces and the Modal Added Coefficients

Submitted by lagrangr on
research
Fluid-structure Interactions

This article addresses the small-amplitude forced beam vibrations of two coaxial finite-length cylinders separated by a viscous Newtonian fluid. A new theoretical approach based on an Helmholtz expansion of the fluid velocity vector is carried out, leading to a full analytical expression of the fluid forces and subsequently of the modal added mass and damping coefficients. Our theory shows that the fluid forces are linear combinations of the Fourier harmonics of the vibration modes.

Article: Modal added-mass matrix of an elongated flexible cylinder immersed in a narrow annular fluid, considering various boundary conditions. New theoretical results and numerical validation

Submitted by lagrangr on
research
fluid structure interaction sub-field discipline fluid mechanics

This paper considers the fluid–structure interaction problem of two coaxial cylinders separated by a thin layer of fluid. The flexible inner cylinder is imposed a small amplitude harmonic displacement corresponding to a dry vibration mode of an Euler–Bernoulli beam, while the external cylinder is rigid. A new theoretical formulation based on the assumption of a narrow fluid annulus is derived to estimate the modal added-mass matrix of the vibrating cylinder.

Article: Hydrodynamic Interaction Between Two Flexible Finite Length Coaxial Cylinders: New Theoretical Formulation and Numerical Validation

Submitted by lagrangr on
research
fluid structure interaction sub-field discipline fluid mechanics

This article addresses the interaction of two coaxial cylinders separated by a thin fluid layer. The cylinders are flexible, have a finite length, and are subject to a vibration mode of an Euler–Bernoulli beam. Assuming a narrow channel, an inviscid and linear theoretical approach is carried out, leading to a new simple and tractable analytical expression of the fluid forces.

Article: New estimations of the added mass and damping of two cylinders vibrating in a viscous fluid, from theoretical and numerical approaches

Submitted by lagrangr on
research
fluid structure interaction sub-field discipline fluid mechanics

This work deals with the small oscillations of two circular cylinders immersed in a viscous stagnant fluid. A new theoretical approach based on an Helmholtz expansion and a bipolar coordinate system is presented to estimate the fluid forces acting on the two bodies. We show that these forces are linear combinations of the cylinder accelerations and velocities, through viscous fluid added coefficients. To assess the validity of this theory, we consider the case of two equal size cylinders, one of them being stationary while the other one is forced sinusoidally.

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