Abstract
The control of vortex-induced vibration (VIV) in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function–vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the fluid, including the mathematical expressions of the lift force coefficient C l , is derived. The initial and boundary conditions as well as the hydrodynamic forces on the surface of cylinder are also formulated. The Lorentz force applied to suppress the VIV has no relationship with the flow field, and involves two categories, i.e., the field Lorentz force and the wall Lorentz force. With the application of symmetrical Lorentz forces, the symmetric field Lorentz force can amplify the drag, suppress the flow separation, decrease the lift fluctuation, and then suppress the VIV while the wall Lorentz force decreases the drag only. With the application of asymmetrical Lorentz forces, besides the above-mentioned effects, the field Lorentz force can increase additional lift induced by shear flow, whereas the wall Lorentz force can counteract the additional lift, which is dominated on the total effect.
Highlights
Bluff structures such as offshore spar, marine risers, overhead transmission lines and heat exchangers are subjected to vortex-induced vibration (VIV) when exposed to a flowing fluid, which contributes to the fatigue life reduction of structures and may produce structure damage under certain unfavorable conditions
The Lorentz force is parallel to the cylinder surface along the flow direction, which leads to the acceleration of the boundary layer fluid and improves the capacity of the fluid for overcoming the adverse pressure gradient
In order to describe the differences between the VIV behavior of the cylinder in shear flow and that in uniform flow, the periodical variation of vortex-induced vibration for different shear rate K
Summary
Bluff structures such as offshore spar, marine risers, overhead transmission lines and heat exchangers are subjected to vortex-induced vibration (VIV) when exposed to a flowing fluid, which contributes to the fatigue life reduction of structures and may produce structure damage under certain unfavorable conditions. The vibrations arise from the time-periodic fluid force associated with the time-periodic shedding vortex, and subsequently alter the flow field, which will change the flow-induced force in turn Such fluid–structure interactions increase the complexity of the fluid mechanisms. For the other, called active control, energy requires to be injected into the flow as moving-wall [28], synthetic jet actuators [29], suction and blowing [30,31,32,33,34] and so on. In in the recent years, the Lorentz force attracted more attention due to investigated its promisingthat the Lorentz force can eliminate the flow separation when the flow past a stationary cylinder, applications in engineering fields. Control of VIV with Lorentz forces for the shear flow has been numerically. Control of VIV with Lorentz forces for the shear flow has been numerically investigated. Lorentz forces is discussed inforces detail.is discussed in cylinder interactions in the shear flow with of different distributions of Lorentz detail
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