Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Experimental Investigation of the Rayleigh Damping Approximation in a Vibrating Catenary Pipe
Submission Author:
André Fujarra , SC
Co-Authors:
Lívia Rampinelli Bozzo, Thiago Antonio Fiorentin, Alexandre Mikowski, Andrea Piga Carboni, André Fujarra, Carlos Duarte de Lemos
Presenter: Lívia Rampinelli Bozzo
doi://10.26678/ABCM.COBEM2023.COB2023-1676
Abstract
This article deals with the Rayleigh method to approximate viscous damping as a combination of inertial and stiffness effects in structures, common in finite element analysis (FEA) programs, such as those that numerically study the dynamics of risers, for example. In slender structures like these, often installed on a free-hanging catenary, it is known that modes of vibration progressively succeed each other until rapid proximity between the natural frequencies at notsohigh order. Therefore, the objective of this work is to experimentally verify whether the Rayleigh method proportional to the linear combination of mass and stiffness in a pipeline launched in a free-hanging catenary is able to adequately represent the viscous damping in a wide range of natural frequencies typically excited by the offshore currents. For this purpose, an 8.6-meter-long pipeline model launched at a height of 6.5 meters in the air and with an angle at the top end of approximately 7 degrees was characterized in terms of its natural frequencies and respective damping coefficients. For measurements, two complementary techniques were adopted: the impact test to obtain the natural frequencies and damping coefficients via the frequency response function (FRF) and the simultaneous tracking of movements along the catenary via a commercial motion capture system (MCS) for characterization of the respective natural modes of vibration. Subsequent comparison of the experimental results with the theory shows that the Rayleigh method is, in fact, a good approximation for the viscous damping of the studied catenary model; however, it is more appropriate when incorporating non-linear proportionality contributions.
Keywords
Rayleigh Damping, Catenary Pipe, modal analysis, Frequency Exciter, Comparisons
