Modal dynamics of structures with bladed isotropic rotors and its complexity for 2-bladed rotors

Abstract. The modal dynamics of structures with bladed isotropic rotors is analyzed using Hill's method. First, analytical derivation of the periodic system matrix shows that isotropic rotors with more than two blades can be represented by an exact Fourier series with 3/rev as the highest order. For 2-bladed rotors, the inverse mass matrix has an infinite Fourier series with harmonic components of decreasing norm, thus the system matrix can be approximated by a truncated Fourier series of predictable accuracy. Second, a novel method for automatically identifying the principal solutions of Hill's eigenvalue problem is introduced. The corresponding periodic eigenvectors can be used to compute symmetric and anti-symmetric components of the 2-bladed rotor motion, and the additional forward and backward whirling components for rotors with more than two blades. Finally, the generic methods are used on a simple wind turbine model consisting of three degrees of freedom for each blade and seven degrees of freedom for the nacelle and drivetrain. The modal dynamics of a 3-bladed 10MW turbine from previous studies is recaptured. Removing one blade, the larger and higher harmonic terms in the system matrix lead to resonant modal couplings for the 2-bladed turbine that do not exist for the 3-bladed turbine, and that excitation of a single mode of a 2-bladed turbine leads to responses at several frequencies in both the ground-fixed and rotating blade frames of reference which complicates the interpretation of simulated or measured turbine responses. </jats:p

Fatigue

La propuesta es reflexionar por las experiencias que atraviesan hombres y mujeres que concurren a espacios destinados a la finalización de la educación general básica en la ciudad de La Plata y su periferia. Interrogarnos por la experiencia puede aportar pistas de análisis que indaguen en los aspectos formativos, en un contexto determinado. La misma puede reservar para un sujeto, cuáles son los modos de comunicarla y de representarla, qué sentidos conlleva, qué disposiciones subjetivas habilita, además de los saberes aprehendidos que involucra. Estas preguntas abren el juego a cuestionamientos relacionados con la desvalorización de las experiencias, surgidas del mundo vital, que se suelen irradiarse desde algunas instituciones. Conjuntamente, esas institucionalidades promueven una maniobra de ubicar en una posición subalterna a los saberes producto de las experiencias, respecto de otros que fueron privilegiados por las estructuraciones surgidas de procesos más encauzados y con dispositivos tangibles, por ejemplo, como la escolarización.The proposal of this work is to reflect about the experiences that men and women go through when they attend to mainstream education institutions from La Plata and its surroundings. Reflecting on this experience could provide us some clues for the analysis of these formative stages, in a given context. Similarly, this could contribute to account for which experiences students are to live, distinct acts of communicating and represent them, which senses are displayed, which subjective dispositions could be habilitated, in addition to the learning knowledge that are involved. These points to be discussed open up the possibilities to ask about the devalue of students´experiences from the vital world, which tend to be irradiated from some institutions. Additionally, these instituting practices promote certain conditions to place the experience knowledge in a subordinated status with respect to that one which was priviledged by structures originated in more channeled processes and tangible devices such as the mainstream education system.Facultad de Periodismo y Comunicación Socia