scholarly journals Fluid Forces on a Circular Cylinder Moving Transversely in Cylindrical Confinement: Extension of the Fritz Model to Larger Amplitude Motions

2006 ◽  
Author(s):  
Cedric Leblond ◽  
Jean-Franc¸ois Sigrist ◽  
Christian Laine ◽  
Bruno Auvity ◽  
Hassan Peerhossaini
Keyword(s):  
Circular Cylinder ◽  
Scientific Literature ◽  
Approximate Analytical Solution ◽  
Finite Amplitude ◽  
Nuclear Industry ◽  
Inviscid Fluid ◽  
Fluid Forces ◽  
Design Engineers ◽  
Perturbation Problem ◽  
Advection Term

This paper is related to the fluid forces prediction on a rapidly moving circular cylinder in cylindrical confinement. The Fritz model, which mainly assumes infinitesimal motions of the inner cylinder in an inviscid fluid, is one of the simplest model available in the scientific literature and is often used by design engineers in the nuclear industry. In this paper, simple non-linear expressions of fluid forces are derived for the case of finite amplitude motions of the inner cylinder. Assuming a potential flow, advection term and geometrical deformations can be taken into account. The problem, formulated as a boundary-perturbation problem, is solved thanks to a regular expansion. The range of validity of the approximate analytical solution thus obtained is theoretically discussed. The results are also confronted to numerical simulations, which allows to emphasize some limits and advantages of the analytical approach.

Transient Fluid Forces on a Rigid Circular Cylinder Subjected to Small Amplitude Motions

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Cédric Leblond ◽  
Vincent Melot ◽  
Jean-François Sigrist ◽  
Christian Lainé ◽  
Bruno Auvity ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Compressible Fluid ◽  
Small Amplitude ◽  
Fluid Model ◽  
The Body ◽  
Analytical Models ◽  
Fluid Forces ◽  
History Effects ◽  
Perturbation Problem ◽  
Dimensional Boundary

The present paper treats the transient fluid forces experienced by a rigid circular cylinder moving along a radial line in a fluid initially at rest. The body is subjected to a rapid displacement of relatively small amplitude in relation to its radius. Both infinite and cylindrically confined fluid domains are considered. Furthermore, non-negligible amplitude motions of the inner cylinder, and viscous and compressible fluid effects are addressed, successively. Different analytical methods and models are used to tackle each of these issues. For motions of non-negligible amplitude of the inner cylinder, a potential flow is assumed and the model, formulated as a two-dimensional boundary perturbation problem, is solved using a regular expansion up to second order. Subsequently, viscous and compressible effects are handled by assuming infinitesimal amplitude motions. The viscous fluid forces are formulated by solving a singular perturbation problem of the first order. Compressible fluid forces are then determined from the wave equation. A nonlinear formulation is obtained for the non-negligible amplitude motion. The viscous and compressible fluid forces, formulated in terms of convolution products, are linked to fluid history effects induced by wave propagation phenomena in the fluid domain. These models are expressed with dimensionless parameters and illustrated for a specific motion imposed on the inner cylinder. The different analytical models permit coverage of a broad range of motions. Hence, for a given geometry and imposed displacement, the appropriate fluid model can be identified and the resulting fluid forces rapidly estimated. The limits of these formulations are also discussed.

Diffraction of impulsive elastic waves by a fluid cylinder

1974 ◽  
Vol 75 (3) ◽  
pp. 391-404 ◽  
Author(s):  
Ramanand Jha
Keyword(s):  
Exact Solution ◽  
Circular Cylinder ◽  
Elastic Medium ◽  
Elastic Waves ◽  
Line Source ◽  
Inviscid Fluid ◽  
Geometrical Theory ◽  
Shadow Zone ◽  
Integral Transformations ◽  
Geometrical Theory Of Diffraction

AbstractIn this paper, the problem of diffraction of an impulsive P wave by a fluid circular cylinder has been considered. The cylinder is embedded in an unbounded isotropic homogeneous elastic medium and it is filled with inviscid fluid material. The line source, giving rise to the incident front, is situated outside the cylinder parallel to its axis.The exact solution of the problem is obtained by using the method of dual integral transformations. The solution is evaluated approximately to obtain the motion on the wave front in the shadow zone of the elastic medium. Further, we interpret the approxi mate solutions in terms of Keller's geometrical theory of diffraction. Our result also gives a correction to an earlier investigation of the similar problem by Knopoff and Gilbert(s).

The Hydrodynamic Forces Acting on a Long Flexible Circular Cylinder Responding to VIV

2006 ◽  
Author(s):  
P. W. Bearman ◽  
F. J. Huera Huarte ◽  
J. R. Chaplin
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Element Model ◽  
Transverse Force ◽  
Diameter Ratio ◽  
Mass Ratio ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Maximum Value ◽  
Vibration Prediction

Distributions of the fluid forces acting along a long flexible circular cylinder free to respond in-line and transverse to a stepped current are presented. Forces are calculated using a finite element model of the cylinder with measured responses providing the input. The length to diameter ratio of the model used was 469, the mass ratio was 3 and the Reynolds number could be varied up to maximum value of approximately 2.6 · 104. Fluid force coefficients for two cases are presented: in the first, the dominant modes are the 2nd cross-flow and the 4th in line. For the second case the leading modes are the 7th and 12th respectively. In general, transverse force coefficients and in-line drag coefficients are found to be larger than those measured for short sections of cylinder undergoing free and forced one and two-dimensional motions. It is anticipated that the results will be of value to developers of vortex-induced vibration prediction methods.

Viscous and inviscid flows in a channel with a moving indentation

1989 ◽  
Vol 209 ◽  
pp. 543-566 ◽  
Author(s):  
M. E. Ralph ◽  
T. J. Pedley
Keyword(s):  
Flow Rate ◽  
Small Amplitude ◽  
Inviscid Flow ◽  
Finite Amplitude ◽  
Navier Stokes ◽  
Inviscid Fluid ◽  
Generation Process ◽  
Vorticity Distribution ◽  
Downstream Flow ◽  
Upstream Flow

The flow in a channel with an oscillating constriction has been studied by the numerical solution of the Navier-Stokes and Euler equations. A vorticity wave is found downstream of the constriction in both viscous and inviscid flow, whether the downstream flow rate is held constant and the upstream flow is pulsatile, or vice versa. Closed eddies are predicted to form between the crests/troughs of the wave and the walls, in the Euler solutions as well as the Navier-Stokes flows, although their structures are different in the two cases.The positions of wave crests and troughs, as determined numerically, are compared with the predictions of a small-amplitude inviscid theory (Pedley & Stephanoff 1985). The theory agrees reasonably with the Euler equation predictions at small amplitude (ε [lsim ] 0.2) as long as the downstream flow rate is held fixed; otherwise a sinusoidal displacement is superimposed on the computed crest positions. At larger amplitude (ε = 0.38) the wave crests move downstream more rapidly than predicted by the theory, because of the rapid growth of the first eddy (‘eddy A’) attached to the downstream end of the constriction. At such larger amplitudes the Navier-Stokes predictions also agree well with the Euler predictions, when the downstream flow rate is held fixed, because the wave generation process is essentially inviscid and the undisturbed vorticity distribution is the same in each case. It is quite different, however, when the upstream flow rate is fixed, as in the experiments of Pedley & Stephanoff, because of differences in the undisturbed vorticity distribution, in the growth rate of the vorticity waves and in the dynamics of eddy A. A further finite-amplitude effect of importance, especially in an inviscid fluid, is the interaction of an eddy with its images in the channel walls.

217 The Characteristics of Fluid Forces Acting on a Circular Cylinder with In-Line Vibrations

2006 ◽  
Vol 2006.45 (0) ◽  
pp. 73-74
Author(s):  
Tooru KINOSHITA ◽  
Hiroshi SAKAMOTO ◽  
Kazunori TAKAI ◽  
Yoshihiro OBATA
Keyword(s):  
Circular Cylinder ◽  
Fluid Forces

Effects of a Few Small Air Bubbles on the Performance of Circular Cylinder at Critical Flow Range in Water

1990 ◽  
Vol 112 (1) ◽  
pp. 67-73 ◽  
Author(s):  
H. Watanabe ◽  
A. Ihara ◽  
S. Onuma
Keyword(s):  
Circular Cylinder ◽  
Drag Coefficient ◽  
Pressure Distribution ◽  
Free Stream ◽  
Water Phase ◽  
Critical Flow ◽  
Test Model ◽  
Air Bubbles ◽  
Turbulence Level ◽  
Fluid Forces

In a horizontal flow channel an experimental study was made on the effects of a small amount of air bubbles on the performance of a circular cylinder at a critical flow range where the drag coefficient of the test model decreased as Reynolds number increased. The measurements of the pressure distribution and fluid forces on the cylinder, the longitudinal turbulence level in water phase and the bubble size distribution in a free stream were taken. The results indicated that a large reduction in the drag coefficient and a change of the pressure distribution around the test model were caused at the low critical flow range by introducing a very small quantity of air bubbles such as 0.05 percent, though the turbulence level in water phase did not increase.

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