Fluid-structure-control interaction simulation of flutter control problems

Flutter is an aeroelastic instability and can lead to destruction of structures, and thus its control is important in engineering. A flutter control problem is classified into fluid-structure-control interaction (FSCI) problems. Conventionally, flutter control has been investigated using simple FSCI models. However, these models are sometimes insufficient because of their many simplifications (e.g., potential flow, simple geometry, small deformation). For control problems with severe nonlinearity, high-fidelity FSCI modeling, where control systems are incorporated into models that couple computational structural dynamics and computational fluid dynamics, may be required. Although high-fidelity modeling has a high computational cost, recent improvements in machine power have made the use of FSCI models feasible. In FSCI analysis, control forces are dealt with as external forces that can be treated implicitly or explicitly. Although the treatment of control forces influences the damping of controlled systems, it has not been discussed in previous studies on FSCI analysis. Furthermore, there has been no study in which high-fidelity FSCI simulations of flutter control problems were conducted. The present study evaluates the difference between the implicit and explicit treatment of control forces using stability analysis. The stability analysis results show that explicit treatment cannot capture the damping of controlled systems, especially for high-order modes. Therefore, implicit treatment is required for FSCI analysis. In numerical examples, we consider flutter of a cantilevered beam in axial flow. Control laws designed using conventional approaches are tested using the developed FSCI analysis. Reasonable results are obtained in terms of the improvement in flutter velocity.

Automated summary

Flutter is an aeroelastic instability that can cause destruction of structures. Its control is crucial in engineering. Previous studies on flutter control have mainly used simplified models, which are sometimes inadequate for highly nonlinear problems. Recent research has shown that high-fidelity modeling, which incorporates control systems into computational structural dynamics and computational fluid dynamics, can be more effective in solving flutter control problems. This study evaluates the difference between implicit and explicit treatment of control forces through stability analysis and finds that implicit treatment is necessary for FSCI analysis.