Aeroelastic analysis of helicopter rotor using virtual blade model and equivalent beam model of a blade

Modern helicopter rotor blades design requires taking into account complex aeroelastic phenomena. Sophisticated computational fluid dynamics and structural dynamics models, available on the market, coupled together enable such analysis with very high fidelity. However, the computational cost of this type of simulation is usually very high and for this reason, it cannot be used in interactive design process or optimization run. Complex Fluid Structure Interaction models are excellent tools for validation purposes, but the design process requires simpler models with lower computational cost and still relatively high accuracy and capabilities. The paper presents a new efficient methodology for calculating helicopter rotor loads, deformations and performance. It uses the well-known Navier-Stokes equations aerodynamic solver – ANSYS Fluent, and modified Virtual Blade Model (based on Blade Element Theory) for rotor flow calculation. This connection guarantees exceptional capabilities and fidelity in comparison with simulation time. The dedicated structural dynamics solver, based on equivalent beam model of a blade and Finite Difference Method, was developed and coupled with CFD part using User Defined Functions in Fluent software. The accuracy of created module was validated with wind tunnel tests data of IS-2 helicopter rotor model, performed in Institute of Aviation. The results of calculations were compared with experimental data for a hover state and a forward flight with three different flight velocities. The comparisons showed very good agreement of the data in most of the analysed cases and pointed out new research possibilities. The presented aeroelastic helicopter rotor model combines all advantages of using three-dimensional Navier-Stokes solver with relatively low computational costs and high accuracy, confirmed by wind tunnel tests. It could be used successfully in helicopter rotor blades design process.