Application of the mixed finite-element method to rotor blade modal reduction

A mixed finite element is investigated as a means for achieving accurate mo dal reduction of rotor blades in finite-element software. A rationale for m ixed finite elements is developed by investigating the modal reduction accu racy of a series of blade analysis methods that introduces, in a step-by-st ep fashion, the key features of the mixed element. During this investigatio n, tile shortcomings of classical, displacement-based finite elements are e xamined qualitatively and through calculations of articulated blade respons e. The formal derivation of the mixed element starting from a mixed variati onal principle is then summarized, and finally, numerical examples are pres ented to demonstrate the element's modal reduction accuracy. (C) 2001 Elsev ier Science Ltd. All rights reserved.