mechanism for vortex-induced vibration attenuation (viv) in low aspect ratio cylindrical structures

摘要

MECHANISM FOR VARTICE-INDUCED VIBRATION ATTENTION (VIV) IN LOW-ASPECT CYLINDRICAL STRUCTURES. The mechanism described in this patent application has as its main objective the attenuation of Vortex Induced Vibration (VIV) in low aspect ratio circular cylindrical structures such as spars and single columns, widely used by the offshore industry in the oil and gas exploration. The design of the VIV attenuation equipment consists of a small diameter two-cylinder autonomous tuning mechanism coupled with systems that allow these cylinders to rotate in a controlled manner near the main cylinder to which VIV is intended to be attenuated. The mechanism is composed of larger (1) and smaller (6) bearings, locating rings (2), flat plate (3), with length (C) restricted to the range between O, 5D and 1.5D, and rotating cylinders (4 ) of diameters (d), defined between O, 05D and O, 15D, making the system also suitable for Vortex Induced Vibration (VIV) attenuation in multidirectional marine currents. The predicted flow velocity for the mechanism operation is defined by the dimensionless Reynolds number (Re), where Re = sym UD / 109, where "p" is the specific mass of the fluid, "U" is the distance flow velocity, "D" is the diameter of the main cylinder and "109" is the dynamic viscosity of the fluid and the VIV attenuator mechanism is intended to function for Re 46.