Bistatic scattering from a stiffened elastic cylinder

Abstract

Submarine hulls are often modeled as stiffened elastic plates at frequencies above the plate coincidence frequency. At lower frequencies, hull curvature and stiffener characteristics become more important. At these frequencies, cylindrical shell and circular beam models may be more appropriate in predicting the acoustic scattered field from stiffened hulls. A theoretical approach is presented describing the bistatic acoustic field scattered from a stiffened elastic cylinder. A finite number of stiffeners are treated as nonuniform translational and rotational modal constraints upon the elastic motion of the fluid‐loaded cylindrical shell. The stiffeners are modeled as curved beams that constrain the shell's three degrees‐of‐freedom at variable locations. This formulation allows the lighter hull rib stiffeners and more massive bulkheads to be considered as an elastic system. For M variably spaced stiffeners, the modal solution depends upon the calculation of seven sets of M(M − 1)/2 cylindrical, fluid‐loaded, cross‐admittance functions and the inversion of a 4M by 4M matrix.