Strain Response and Aerodynamic Damping of a Swirl Distortion Generator Using Computational Fluid Dynamics

The need for more efficient and environmentally sustainable aircraft has been a rapidly increasing topic for research and development over the last few decades. Industry and NASA’s Glenn Research Center have been extensively testing Boundary Layer Ingestion (BLI) principles on propulsion systems. BLI has statistically shown to increase aircraft fuel efficiency by reducing overall drag and increasing thrust generation by reenergizing the aircraft wake. The StreamVane™ system, developed by Virginia Tech, is a secondary flow distortion generator that can be used to simulate air flow at the aircraft boundary layer. In turn, this provides time and cost efficient testing methods to evaluate the aeromechanics of turbomachinery components due to BLI. To allow for this efficiency, StreamVanes are manufactured using the thermoplastic resin ULTEM 9085. The raw material properties of this resin suggest that StreamVanes are sufficient enough to withstand aerodynamic loads encountered during testing conditions. However, in a particular experiment, a vane within the StreamVane geometry might have failed under certain conditions. A better understanding of the aerodynamic properties of this system needs to be ensured for the safety of the test engines. A one way fluid structure interaction (FSI) through ANSYS Mechanical and CFD software will first be done. Unsteady CFD methods are used to accurately predict the fluid flow in the StreamVane system at multiple mass flow rates. Using the pressure loading acquired from the CFD, a pre-stressed Modal Analysis is performed to obtain the mode shapes and natural frequencies of the StreamVane. The mass flow rate that excites the most amount of modes is used to computationally determine each vane’s strain response within the StreamVane. The modal transformation method is used to evaluate this strain response and reduce it to a specific number of active degrees of freedom. These active points will provide insight on where to measure the strain response during experiment to validate the results. 

Secondly, a flutter analysis is then conducted on the reduced StreamVane model. The steady CFD solution and mode shapes obtained in the previous results will be prescribed to a second transient CFD analysis. Once these unsteady solutions are calculated, aerodynamic damping coefficients of the vanes can be determined from the motion and forces throughout the simulation. Given the computational prediction of aerodynamic damping and flutter, the knowledge of aeroelastic failure within a StreamVane will be known. These results will provide a better understanding of the aerodynamic properties of this system and further experiments will be held to validate the results.