Showing papers by "Earl H. Dowell published in 1979"

An Elementary Explanation of the Flutter Mechanism with Active Feedback Controls

Abstract: An elementary explanation of wing flutter suppression problems with active feedack control is made using a standard root locus technique. The object of the study is to obtain insight into the control of converging frequency flutter such as the classical bending-torsion flutter of a wing. The model analyzed is a twodimensional, typical section airfoil with pure gain feedback of the main wing motion. In this simple system, stability boundary solutions are expressed in a closed form and valuable information is obtained for various kinds of feedback signals. The results for an exploratory example are discussed. The analysis of this example using Nissim's energy method is also attempted.

Master Plan for prediction of vehicle interior noise

Abstract: Substantial advances have been made in improving the analytical methods available for prediction of interior noise and providing an experimental data base for their assessment and validation. A review of recent accomplishments, including representative results, is presented in the context of a Master Plan. It is suggested that modal representations of structural walls and acoustic cavities provide a useful conceptual and computational theoretical framework for including the mass, stiffness and damping of both the structure and acoustic cavity. Geometrical details and acoustic damping (absorption) are included in a rigorous manner. Future efforts, both near term and long term, are identified which are required to complete the Master Plan and provide the noise control practitioner with access to these improved methods.