A Mode Based Reduced Order Model for Rotorcraft Store Separation

Abstract

Store separation from aircraft and spacecraft has been a critical, and in some cases problematic, issue for the aerospace industry. However, the procedures currently used for identifying potential failure conditions are both resource intensive and time consuming. A potential remedy to reducing resources and to improve turn around time in this process is the construction of a mode based reduced order model (ROM) that can be utilized for fast and accurate modeling of store separation. The objective of this study was to utilize the mode based reduced order model for two subtask; load prediction and trajectory prediction. To analyze the ROMs capability for load prediction, a preliminary study for modeling hysteresis loops of an oscillating store was pursued first. This model was based on a series of twelve simulations covering a range of two oscillation parameters. Two models were constructed, one through a series of 2-D surface mappings and another through Kriging interpolation of the surface pressure distribution. Through a comparison of ROM and CFD-simulation at three combinations of reduced frequencies and amplitudes the resulting model was able to make accurate load predictions for intermediate reduced frequencies and amplitudes in the training data range at a negligible computational cost. In an attempt to investigate the ROMs ability to predict store trajectories of intermediate conditions, three cases of store separation at Mach 0.5, 0.8, and 1.2 were considered. Prediction of trajectories at an intermediate Mach numbers can be accomplished using the ROM-based model constructed from computed store separations at Mach 0.5, 0.8, and 1.2. Results showed a close agreement between CFD and ROM trajectory predictions. The model predictions can encompass more parameters and the computational cost of the model will still remain negligible compared to the full CFD simulation.