Reduced-Order Modeling of Flow-Induced Vibrations in Bellows Joints of Rocket Propulsion Systems

摘要

For nearly a half century, there has been sporadic research Interest in flow-induced vibration (FIV) of bellows expansion Joints. Bellows expansion joints are commonly used in rocket propulsion systems to allow for articulation and to reduce misalignment loads In both fuel and oxidlzer lines. However, these joints are susceptible to a high-amplitude FIV phenomenon that can compromise the structural Integrity of the joint. To date, there does not exist a physics-based method of predicting this complex fluid-structure Interaction (FSI) phenomenon. The current empirically-based method used by NASA to assess FIV in bellows joints was developed in the early 1980s. Presently, new bellows designs are testing the limits of this historical method, underscoring the need for a more modern approach that is computationally efficient and physically insightful. To accomplish this, we propose a FSI model that couples a discrete mechanical model of the bellows to a van der Pol oscillator equation modeling fluid wake. This method reduces the computational expense of the problem by several orders of magnitude relative to high-fidelity FSI simulations and enables the efficient characterization of bellows FIV across a large design space. The model has potential to be a useful design tool as it predicts FIV amplitude response and frequency lock- in behavior. A comparison of the model output to experimental bellows response data shows good agreement.