A longitudinal vibration coupling with a flexural vibration in a curved fluid-filled periodic pipe is studied. The pipe is fabricated by a periodic composite material structure based on the Bragg scattering mechanism of Phononic Crystals. Using the transfer matrix method, the band structure of an infinite periodic straight pipe is calculated, and the elastic wave propagation characteristics of the periodic pipe are discussed. Furthermore, the vibrational frequency response functions of a finite curved pipe are performed and the coupled vibration is studied. Finally, the transmission properties of longitudinal vibration, flexural vibration and their coupling vibration in the curved periodic fluid-filled pipe are investigated.
In order to improve the treatment efficiency of the constrained layer damping (CLD), it is meaningful to have a study on its layout optimization. This paper based on current research of Cellular Automata (CA) algorithm for CLD optimization, points out that the current application of CA algorithm is less efficient, considering that adding or deleting a single CLD patch almost does no change to the entire structure, then makes a simplification and modification of CA algorithm. With the aim at improving the structural modal loss factor, this paper uses the current CA algorithm and its modified algorithm to optimize a partial CLD plate. The results have shown that the modified CA algorithm for CLD optimization can not only substantially increase computing efficiency, but to some extent, improve the optimization effectiveness.
Rain-wind induced vibration (RWIV) is a violent oscillation that appears on cable stayed bridge under rainy weather. Many researchers agree that the rivulets (specially the upper one) play an important role during the vibration. In present work, the upper rivulet’s effect is focused. A circular cylinder with an arches attachment on its surface is modeled to take the place of cable- rivulets system section in RWIV. Using finite volume method (FVM), 3D Flow past the cylinder-arch model is simulated for subcritical Reynolds Number (Re, ≈6.8×104). Large Eddy Simulation (LES) method is drawn in as a closure of turbulence model. The attachment locating at different positions are calculated. The results show many differences between cylinder-arch model and bare circular cylinder, including force coefficients change dramatically and velocity distributions in wake zone vary remarkably. Responses of cylinder-arch system driven by aerodynamic forces are also studied. Fourth order Runge-Kutta Method is introduced to solve second order ODEs that describe the vibration of cylinder model. The first four modal response are calculated and then added to analyze cable oscillating properties.
The effects of tripping rods on characteristics and fluid forces acting on a single cylinder was three-dimensional numerical studied in a low laminal flow at a Reynolds number of 200 and a subcritical stream at a Reynolds number of 5.5X104. The angular position of the tripping rods was varied from 20 to 60.The results reveal that there exits an optimum position of tripping rod for reducing fluid forces. This optimum angular position was found to be 40° for Re=200 and 30° for Re=5.5X104. At this optimum angle, the steady drag, fluctuating drag and fluctuating lift forces acting on the cylinder are reduced by 21%, 32%, and 28% for Re=200 and 36%, 44%, 76% for Re=5.5X104.
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