NASA’s Langley Research Center has developed unsteady aerodynamic Reduced-Order Models (ROMs) that significantly improve computational efficiency compared to traditional analyses of aeroelastic and other complex and unsteady systems. Traditional methods rely on the repetitive use of aeroelastic computational fluid dynamics (CFD) codes, and the iteration between the structural and nonlinear aerodynamic models of the aeroelastic CFD code for predicting the aeroelastic response of flight vehicles is very time-consuming and computationally expensive. The new ROMs are quite different from the traditional aeroelastic analysis tools, and enable the computational aeroelastic analysis of flight vehicles at a fraction of the time and cost.
Traditional computational aeroelastic analysis using CFD codes requires the coupled interaction of the linear structural model and the nonlinear aerodynamic model (both within the aeroelastic CFD code). The structural model provides displacements due to aerodynamic forces, and the nonlinear aerodynamic model computes the aerodynamic forces induced by the structural displacements. The computed aerodynamic force is passed back to the structural model, and the resource-intensive process is repeated at each time step.
Starting with an aeroelastic model consisting of a CFD grid and structural mode shapes, NASA Langley’s new analysis procedure occurs as follows:
- The unsteady aerodynamic responses of all of the structural modes are computed by exciting all of the modes simultaneously in just one execution of the CFD code.
- The responses obtained in Step 1 are processed through a NASA Langley-developed set of algorithms, yielding a simplified mathematical model in state-space form.
- The state-space forms of the aeroelastic and structural models are combined, and a new method computes matched-point solutions. Another new method enables simultaneous computation of the static and dynamic responses.
This technology can be used in aerospace applications for aerodynamic flutter of rotorcraft, and in civil structures for dynamic behavioral models of large buildings and other civil structures such as bridges, dams, and towers.