Force coefficients and Strouhal numbers of four cylinders in cross flow

2003 ◽  
Vol 18 (3-4) ◽  
pp. 305-324 ◽  
Author(s):  
K Lam ◽  
J.Y Li ◽  
R.M.C So
Keyword(s):  
Cross Flow ◽  
Force Coefficients ◽  
Four Cylinders

Measurement of Flow-Induced Forces: A Single Flexible Tube in a Rigid Triangular-Pitch Bundle Subjected to Two-Phase Cross-Flow

2015 ◽  
Author(s):  
Enrico Deri ◽  
Joël Nibas ◽  
Olivier Ries ◽  
André Adobes
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Tube Bundle ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Maintenance Policy ◽  
Excitation Spectra ◽  
Two Phase ◽  
Force Coefficients ◽  
Out Of Plane

Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators of nuclear power plants. In order to predict damages due to such vibrations, EDF has developed the numerical tool GeViBus, which allows one to asses risk and thereafter to optimize the SG maintenance policy. The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be assessed by experiment. The database of dimensionless coefficients is updated in order to cover all existing tube bundle configurations. Within this framework, a new test rig was presented in a previous conference with the aim of assessing parallel triangular tube arrangement submitted to a two-phase cross-flow. This paper presents the result of the first phase of the associated experiments in terms of force coefficients and two-phase flow excitation spectra for both in-plane and out-of-plane vibration.

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.

Model Test on Drag of Cylinders With Helical Grooves at High Reynolds Numbers

2010 ◽  
Author(s):  
Shan Huang ◽  
Neil Kitney
Keyword(s):  
Model Test ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Tank Model ◽  
Towing Tank ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Helical Grooves ◽  
Four Cylinders

Towing tank model tests at high Reynolds numbers, up to 1.1×106, were carried out in order to investigate the effects of the triple-starting helical grooves on drag reduction of smooth and rough circular cylinders in uniform cross flow. In total, four cylinders were tested including smooth and rough cylinders with and without helical grooves.

Streamwise Fluidelastic Forces in Tube Arrays Subjected to Two-Phase Flows

2014 ◽  
Author(s):  
Stephen Olala ◽  
Njuki W. Mureithi ◽  
Teguewinde Sawadogo ◽  
Michel J. Pettigrew
Keyword(s):  
Flow Direction ◽  
Cross Flow ◽  
Force Coefficient ◽  
Two Phase ◽  
Fluid Force ◽  
Phase Measurements ◽  
Force Coefficients ◽  
Void Fractions ◽  
Drag And Lift ◽  
Unsteady Fluid

Detailed unsteady fluid force and phase measurements for a single tube oscillating purely in the streamwise direction in a rotated triangular tube array subjected to air-water two-phase cross-flow have been conducted in this study for homogeneous void fractions between 0% and 90%. Additionally the streamwise steady forces were measured in two-phase flow at a Reynolds number (based on the pitch velocity), Re = 7.2 × 104. The results are compared to those previously obtained for transverse direction oscillations. The measurement results show that the magnitude of the force coefficients for both directions (drag and lift) is comparable both in trend and quantitatively. However, the phase in the drag direction is negative while that for the lift is positive. The range of variation of the phase is also significantly smaller for the drag direction. Noting that negative phase corresponds to positive damping and vice versa, this observation confirms previous findings of lack of instability in the drag direction for a single flexible tube in a rotated triangular tube array. The drag steady fluid force coefficients were found to increase with dimensionless displacement in the flow direction for the entire range of void fractions considered. The derivative of the measured steady fluid force coefficient, which is an important factor in fluidelastic instability study using the quasi-steady model, was found to remain positive in the drag direction. The effect of void fraction on the unsteady fluid force coefficient and other dynamic parameters such as hydrodynamic mass and damping are also discussed.

A Lattice Boltzmann Simulation of Cross-Flow Around Four Cylinders in a Square Arrangement

2010 ◽  
Author(s):  
J. Abolfazli Esfahani ◽  
A. R. Vasel Be Hagh
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Lattice Boltzmann ◽  
Cross Flow ◽  
Spacing Ratio ◽  
Volume Method ◽  
Boltzmann Method ◽  
Four Cylinders

The purpose of the present work is simulating cross flow around four cylinders in a square configuration by using a Lattice Boltzmann method. The effective parameters such as Reynolds number and spacing ratio L/D are chosen on the basis of former researches of other authors which have been done experimentally or by using traditional numerical schemes like finite volume method to provide the opportunity for comparing Lattice Boltzmann results with those obtained from experimental and CFD studies. Hence, the Reynolds number is set at Re = 100 and the spacing ratio is chosen to be 1.5, 2.5, 3.5, 4.5. It is shown that final results such as flow pattern, velocity and vorticity field are in accordance with those obtained by former researchers via experimental efforts or by use of finite volume method. This good agreement beside other important qualities such as efficient code, not having mesh tangling associated with other common numerical approaches, high convergence speed and nondimensional velocity and pressure field indicate this fact that in comparison with other numerical methods, Lattice Boltzmann method is very capable of analyzing a broad variety of fluid flows.

scholarly journals Flow-Induced Vibration of Tubes in Cross-Flow

1996 ◽  
Vol 118 (4) ◽  
pp. 253-258 ◽  
Author(s):  
S. S. Chen ◽  
Y. Cai ◽  
S. Zhu
Keyword(s):  
Unsteady Flow ◽  
Mathematical Models ◽  
Cross Flow ◽  
Flow Theory ◽  
General Description ◽  
Flow Induced Vibration ◽  
Fluid Force ◽  
Force Coefficients ◽  
Fluid Forces

This paper presents an unsteady-flow theory for flow-induced vibration of tubes in cross-flow. It includes a general description of motion-dependent fluid forces, characteristics of fluid-force coefficients, and mathematical models. Detailed results are presented for the constrained mode in the lift direction for various tube arrangements.

Hydrodynamic Forces on Pipelines: Model Tests

1992 ◽  
Vol 114 (4) ◽  
pp. 231-241 ◽  
Author(s):  
M. B. Bryndum ◽  
V. Jacobsen ◽  
D. T. Tsahalis
Keyword(s):  
Cross Flow ◽  
Hydrodynamic Forces ◽  
Irregular Waves ◽  
Regular Waves ◽  
Force Coefficients ◽  
Steady Current ◽  
Sea Bottom ◽  
Least Squares Fit ◽  
Wide Range ◽  
Flow Directions

An extensive model test program on the hydrodynamic forces on a submarine pipeline resting on the sea bottom and exposed to steady current, regular waves, combined steady current and regular waves, irregular waves, and combined steady current and irregular waves has been performed. The hydrodynamic forces in both the in-line and the cross-flow directions have been analyzed using three different methods, i.e., least-squares-fit analysis based on Morison-type equations, Fourier analysis, and maximum force analysis. The force coefficients associated with each method have been determined for a wide range of environmental conditions. The results of the tests are presented in terms of the calculated force coefficients and their dependence on various nondimensional parameters is discussed. Furthermore, comparisons with other test data are presented.

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