Unsteady Pressure Analysis of an Oscillating Cylinder Exhibiting Non-Synchronous Vibrations
When an unsteady aerodynamic instability interacts with the natural modes of vibration of a rigid body, lies a phenomenon known as Non-Synchronous Vibrations (NSV), often referred to as Vortex-Induced Vibrations (VIV). These vibrations cause blade failure in jet engines; however, the underlying flow physics are much less understood than other aeroelastic phenomenon such as flutter or forced response. When the buffeting frequency of the flow around a body nears a natural frequency of said body, the former frequency “locks in” to the latter. Within this “lock in” region there is only one main frequency, while outside of it there are two. Although this phenomenon has been documented both experimentally and computationally, the unsteady pressures associated with this phenomenon have not been accurately measured. First, we collected the spectra of pressure frequencies around a circular cylinder exhibiting NSV using computational fluid dynamics. Then, time domain pressure data is Fast Fourier Transformed to provide frequency domain data. Finally, the data analyzed as well as validated against experimental results as well as other numerical models, providing good agreement. Understanding the unsteady pressures and how they affect the flow physics of NSV allows for further studies into this phenomenon, paving the way for the design of more efficient and powerful engines.
