Advanced Models for Aeroelastic Analysis of Propulsion Systems
This report describes an integrated, multidisciplinary simulation capability for aeroelastic analysis and optimization of advanced propulsion systems. This research is intended to improve engine development, acquisition, and maintenance costs. One of the proposed simulations is aeroelasticity of blades, cowls, and struts in an ultra-high bypass fan. These ducted fans are expected to have significant performance, fuel, and noise improvements over existing engines. An interface program was written to use modal information from COBSTAN and NASTRAN blade models in aeroelastic analysis with a single rotation ducted fan aerodynamic code.
Semi-empirical model for prediction of unsteady forces on an airfoil with application to flutter
Abstract A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modelled using second-order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter, Comparison is made to the flutter characteristics determined by a Navier-Stokes solver also the classical incompressible potential flow theory.
Matching the Implant to the Breast: A Systematic Review of Implant Size Selection Systems for Breast Augmentation
Background: For primary breast augmentation, several implant selection systems have been described to guide the surgeon with choosing from a variety of manufactured implant dimensions and properties. Controversy exists regarding the most efficacious method of selecting an appropriate implant size that best matches the patient’s breast. Methods: The goal of this systematic review was to provide a comprehensive list of documented implant size selection systems, and to critically evaluate them. Implant size selection systems were grouped into categories based on selection principles. Articles were evaluated based on reported outcome measures and methodologic quality. Results: Thirty-three implant size selection systems were included in the final analysis. Only 12 percent of articles (four of 33) reported clinical outcomes that could be compared to accepted literature values or industry standards. Articles that described tissue-based planning systems, which use clinical guidelines to determine the optimal patient-specific implant dimensions, were of highest methodologic quality using the Methodological Index for Non-Randomised Studies scale, when compared to systems that used breast “dimensional” analyses that stress tissues to the desire of the patient and/or surgeon, and compared to systems that did not use breast measurement (means ± SD, 6.0 ± 1.4, 1.4 ± 2.3, and 0.0 ± 0.0, respectively). Conclusions: There is some evidence to support tissue-based planning as a superior approach to implant size selection planning; studies that used tissue-based planning reported lower reoperation rates compared with industry standards and accepted literature values. The authors offer several suggestions on how to improve the methodologic quality of future studies describing new implant selection systems.