Proposal for analyzing energy dissipation mechanisms to improve fidelity of acoustic scattering predictions

Anticipated computing advances will greatly enhance the Navy's ability to compute submarine target strength. This capability can be an important diagnostic and design tool for T.S. control. While the complexity and size of the scattering problem makes it necessary to solve large sets of structural-acoustic equations, especially at mid-frequencies, it is not sufficient to achieve high fidelity predictions. A number of other outstanding issues must be resolved. One is the lack of mathematical descriptions of the dominant energy dissipation mechanisms associated with hull and internal structure vibrations other than acoustic radiation. Such mechanisms include dry friction or Coulomb damping, viscous damping, e.g., of flexural waves, isolation mounts, and at stress concentration, air damping etc. Regardless of computing power this limits the fidelity of predictions for those T.S. components affected by submarine elasticity; the launching, propagation and scatteing of elastic waves. It is the purpose of the proposed Phase I work to ameliorate this situation by identifying candidate mechanisms, developing mathematical descriptions for their behavior, criteria for required input parameters, and providing solution techniques compatible with conventional structural-acoustic numerical methods.