Structural-Acoustic Modeling and Optimization of a Submarine Pressure Hull

The Energy Finite Element Analysis (EFEA) has been validated in the past through comparison with test data for computing the structural vibration and the radiated noise for Naval systems in the mid to high frequency range. A main benefit of the method is that it enables fast computations for full scale models. This capability is exploited by using the EFEA for a submarine pressure hull design optimization study. A generic but representative pressure hull is considered. Design variables associated with the dimensions of the king frames, the thickness of the pressure hull in the vicinity of the excitation (the latter is considered to be applied on the king frames of the machinery room), the dimensions of the frames, and the damping applied on the hull are adjusted during the optimization process in order to minimize the radiated noise in the frequency range from 1,000Hz to 16,000Hz. Constraints on the total amount of damping that can be used are considered (resource driven constraints) and structural collapse constraints are also taken into account in order to avoid degrading the structural integrity of the pressure hull. Two different optimization strategies are exercised. First a concurrent multidisciplinary analysis is performed; optimal configurations for structural performance and for acoustic radiation are identified and the results are used for producing a single design with optimized performance in both disciplines. Then, an analysis based on set-based design principles is performed. The latter identifies several alternative and diverse hull configurations that provide similar levels of performance with respect to the radiated noise. Having several alternative solutions of nearly equal performance provides insight into the design trade-offs when configuring the pressure hull. The results from both optimization strategies are analyzed and discussed.