An improved linear model for rotors subject to dissipative annular flows

A Symbolic-Numerical Method for Nonlinear Rotor Dynamics under Fluid Confinement

“…In this figure one can also, see superimposed solid lines corresponding to the modal frequency and damping curves, computed from the linear model developed recently by Moreira et al [17]. The solid lines display, respectively, the frequency ^ and the damping -σ η , where un and ση are the imaginary and real parts of the complex eigenvalues λ" = σ η 4-iv n of the linearized improved model.…”

“…Linear theory predicts instability at about 510 rpm. Note that the modal curves show an additional zero-frequency mode, discussed in [17], which is related to the co-rotating flow.…”

Study on critical speed of rotation in the multistage high speed centrifugal pumps rotors

“…Scholars have done a lot of work to precisely predict the dynamic characteristics of the rotor system. Similar to the oil film bearing simulation, there are some scholars such as Tian Yabin [9], Antunes [10,11], Sun Qiguo [12] studied the dynamic coefficient of the eccentric rotor when the fluid machinery soaked in the circulation fluid in the big gap. However, the fluid-structure interaction mechanism in the rotor system is much different from the oil film bearing, the dynamic coefficient is not appropriate for describing the dynamic characteristics of the rotate system.…”

A theoretical model and experiments on the nonlinear dynamics of parallel plates subjected to laminar/turbulent squeeze-film forces

“…gap hðr,tÞ ¼ hðrÞþhðr,tÞ is small compared to the mean gap value hðrÞ-see, for instance, works by Fritz (1970), Hobson (1982), Mulcahy (1980Mulcahy ( , 1988 or Moreira et al (2000a), as well as the review books by Païdoussis (1998) and Kaneko et al (2008). One of the most thorough analyse along these lines was achieved by Hayama (1990a, 1990b), who evaluated the fluidelastic force under steady flow, including added mass, damping and stiffness flow terms for a onedimensional tapered leakage channel.…”

“…However, our previous dynamical solution will be now extended in order to encapsulate, in the analytical formulation of the nonlinear fluid coupling force, the flow velocity dependence of the dissipative terms. Overall, the analytical formulation developed here may be connected with our approach in work focused on immersed rotor dynamics-see Axisa and Antunes (1992), Grunenwald (1994), Antunes et al (1996Antunes et al ( , 1999, and Moreira et al (2000aMoreira et al ( , 2000b. Indeed, the successful ''bulk-flow'' approach started by Fritz (1970) and Hirs (1973), and later used by many authors -see Childs (1993) -appears also well suited to deal with the small-tomoderate fluctuating gaps, such as found in the configuration of the present problem.…”