CFD-CSD Support for Rotor Design Improvement to Reduce Vibrations

Abstract

This paper demonstrates the recent success of applying advanced modeling and simulation digital tools to guide rotor design update to achieve a reduced vibration and an increased aerodynamic performance at high speed flight conditions. To understand and improve the vibration characteristics of the coaxial rotor configurations, a multi-year effort has been invested to develop a fully coupled Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) methodology. The developed tool has been validated with early flight test data from the S-97 RAIDER® aircraft. The validated tool is then applied to carryout extensive design trade studies across a wide range of design variables. The goal is to gain a fundamental understanding of the coaxial rotor vibration physics and to identify practical design updates to achieve a reduced rotor vibration without adversely impact rotor aerodynamic performance. Therefore, impact of key design attributes on rotor aerodynamic performance is also being studied in parallel. Based on the design trade studies and considering manufacturing, cost and schedule, an updated rotor blade design is proposed and manufactured. Flight test of the updated rotor design confirmed the predicted reduction in rotor vibration and increase in rotor cruise performance. This study shows that using the current state-of-the-art methodology, when carefully validated and applied, can capture the complex rotor vibration physics due to fluid and structure interaction with sufficient accuracy to support the X2 Technology™ configurations.