A numerical study on fluid elastic vibrations of multiple cylinders in cross flow

Abstract

The flow-induced vibrations of cylinder arrays subjected to cross flow are studied numerically. Multiple cylinders, two to seven identical cylinders, in a rotated triangular array are investigated, with an emphasis on neighborhood-cylinder effects on the onset of fluid elastic vibrations for a monitored cylinder. The instantaneous velocity and pressure distributions of the fluid flow, and the fluid forces on cylinder surfaces are computed numerically. The displacements of the cylinders, due to the fluid forces, are then calculated as a function of time, to describe the cylinder motions in the flow. From the amplitude responses of the cylinders, it is illustrated that fluid elastic vibrations with significant amplitude occur in multiple cylinders as the freestream velocity goes beyond a critical value, while a single cylinder can only exhibit vortex-induced vibrations with relatively small amplitude in a narrow velocity range. Beyond the critical velocity, the cylinders vibrate in elliptical orbits. Amplitude diagrams are used to determine the critical velocity for the onset of the fluid elastic vibrations. It is shown that with more upstream cylinders, the critical velocity of the monitored cylinder decreases, implying that the cylinder becomes more fluid elastically unstable. However, the critical velocity of the cylinder does not change as more adjacent cylinders are added downstream.

Numerical simulation of vortex induced vibration in heat exchanger tube bundle at low Reynolds number

“…Fig. 10, 11 and 12 show the results of coefficient of lift, drag and Strouhal number over the tube and validated withYu and Lin (2005).…”

“…Basically the standard k-epsilon model represents the flow near to the wall by resolving the flow parameters without any mathematical representation of the flow profiles using the wall function approach. Thus, Low-Reynolds number requires finer mesh and a smaller y + value, depending on the Reynolds number of the flow Yu and Lin (2005). The y + value is 5mm.…”

“…Strouhal number has been calculated by using the C L amplitudes. The coefficient of Lift amplitudes varies along zero (Yu andLin, 2005 andRahman et al, 2007). There are 20,000 iterations where there is a same amplitude in C L .…”

“…According to Chenoweth et al (1993), for a single cylinder Strouhal number is a constant with a value of about 0.2. Kevlahan (2011) simulation over the single cylinder reviews the generation of lift force over the cylinder due to vortices at higher Reynolds numbers (R e ). Yu and Lin (2005) pointed out that beyond the critical value of free steam velocity a single cylinder can show a large amplitude response even with a small velocity change.…”

“…Kevlahan (2011) simulation over the single cylinder reviews the generation of lift force over the cylinder due to vortices at higher Reynolds numbers (R e ). Yu and Lin (2005) pointed out that beyond the critical value of free steam velocity a single cylinder can show a large amplitude response even with a small velocity change. There is a certain vibration of the cylinder in elliptical orbits beyond the critical value.…”