Appendix Q Viscous force coefficients for cylinders in axial flow

Author(s):  
Ahmad Jamal ◽  
Michael P. Païdoussis ◽  
Luc G. Mongeau

Understanding and prediction of the dynamics of slender flexible cylinders in axial flow is of interest for the design and safe operation of heat exchangers and nuclear reactors, specifically that of heat exchanger tubes, nuclear fuel elements, control rods, and monitoring tubes. In such fluid-structure interaction problems, the fluid forces acting on the flexible structure play a vital role in defining its dynamics. Therefore, a precise calculation of the coefficients associated to these forces, such as the longitudinal and normal viscous force coefficients, and base drag coefficient in the equation of motion is imperative. The present work is aimed at (i) calculating these force coefficients for a cantilevered slender flexible cylinder, fitted with an ogival end-piece, in axial flow and (ii) conducting experiments on the same system. In the calculation of these force coefficients, the parameters of the experimental system are used, so that the theoretically predicted dynamics would be representative of the actual physical system. These calculated force coefficients are then incorporated in the linear and nonlinear equations of motion and the predicted dynamics are compared with those of the experiments. The comparison shows good agreement between the theoretical and experimental results.


2011 ◽  
Vol 99-100 ◽  
pp. 1059-1062
Author(s):  
Ji Duo Jin ◽  
Ning Li ◽  
Zhao Hong Qin

The nonlinear dynamics are studied for a supported cylinder subjected to axial flow. A nonlinear model is presented for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain the flutter instability found in the experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the new equilibrium (the buckled configuration) becomes unstable at higher flow leading to post-divergence flutter. The effect of the friction drag coefficients on the behavior of the system is investigated.


2011 ◽  
Vol 117-119 ◽  
pp. 295-298
Author(s):  
Ji Duo Jin ◽  
Ning Li

The stability of a supported cylinder subjected to axial flow is studied numerically. The dynamics of the cylinder is investigated with the numerical method applying the new nonlinear model in witch the nonlinear terms considered are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using three-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder. Some integration terms that appear in the discretization of the equation and can not be expressed in an analytical form are calculated using a numerical method. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence and at a higher velocity the flutter around the zero equilibrium may occur. There is some region in witch three different motions (configurations) can take place at the same parameter values.


2011 ◽  
Vol 130-134 ◽  
pp. 761-765
Author(s):  
Ji Duo Jin ◽  
N. Li ◽  
Zhao Hong Qin

The stability and nonlinear dynamics are studied for a slender flexible cylinder subjected to axial flow. A nonlinear model is presented, based on the corresponding linear equation of motion, for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the additional axial force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain, with this relatively simple nonlinear model, the flutter instability found in experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the buckled configuration becomes unstable at higher flow leading to post-divergence flutter. As the flow velocity increases further, the system is restabilized in the buckled configuration prior to another dynamic instability at higher flow.


2012 ◽  
Vol 60 (S 01) ◽  
Author(s):  
P Ganslmeier ◽  
HJ Schneider ◽  
A Keyser ◽  
M Michl ◽  
M Foltan ◽  
...  

Waterlines ◽  
1989 ◽  
Vol 8 (2) ◽  
pp. 10-12 ◽  
Author(s):  
Stickney ◽  
Salazar
Keyword(s):  

2017 ◽  
Vol 137 (1) ◽  
pp. 30-35
Author(s):  
Hiroaki Narita ◽  
Makoto Saruwatari ◽  
Jun Matsui ◽  
Yasutaka Fujimoto

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