Vibration Analysis of Pre-Twisted Blades with Symmetric and Asymmetric Airfoils Using the Ritz Method

Shokrollahi, Saeed; Norouzi, Alireza; Shafaghat, Salman

doi:10.22064/tava.2026.2074533.1277

Vibration Analysis of Pre-Twisted Blades with Symmetric and Asymmetric Airfoils Using the Ritz Method

Document Type : Research Article

Authors

Saeed Shokrollahi ¹

Alireza Norouzi ²

Salman Shafaghat ²

¹ Malek E Ashtar University of Technology

² Malek Ashtar university of Technology, Aerospace Engineering Department

10.22064/tava.2026.2074533.1277

Abstract

This study performs a theoretical free vibration analysis of pre-twisted rectangular and airfoil-section blades using a global Ritz-based continuous classical beam–shaft reduced-order model (ROM), demonstrating its applicability in gas turbine design workflows. The framework incorporates pre-twist effects and static imbalance (CG–EA offset), which is horizontal in symmetric airfoils and also vertical in cambered or asymmetric airfoil sections. Validation is performed against finite element method (FEM) analyses using MSC Nastran and results from an advanced finite difference method (FDM) reported in the literature. The results show strong agreement with other works while maintaining computational efficiency. The proposed framework provides a basis or ROM-based tools capable of performing computationally efficient aeroelastic analyses of continuous blade models, blade rows, and integrated gas turbines. Torsional, flapwise, and chordwise bending modes—including their couplings induced by pre-twist and static imbalances—are examined, and natural frequency trends for different imbalance configurations are presented as functions of pre-twist angle

Keywords

Free Vibration

Blade

Pre-twist

Ritz method

Subjects