External mean flow effects on noise radiation from orthogonally rib-stiffened aeroelastic plates

A theoretical modeling approach is proposed for noise radiated from aeroelastic skin plates of aircraft fuselage stiffened by orthogonally distributed rib-stiffeners and subjected to external jet-noise in the presence of mean flow. The focus is placed upon quantifying the effects of mean flow on the aeroelastic-acoustic characteristics of the ribstiffened plate. The Euler-Bernoulli beam equation and the torsional wave equation governing separately the flexural and torsional motions of the rib-stiffeners are employed to accurately describe the force-moment coupling between the stiffeners and the plate. Given the periodicity of the structure, the resulting governing equations of the system are solved by applying the Poisson summation formula and the Fourier transformation technique. The radiated sound pressure is related to the plate displacement by means of the Helmholtz equation and the fluid-structure boundary conditions. To highlight the radiation characteristics of the periodically stiffened structure as well as the mean flow effects, the final radiated sound pressure is presented in the form of decibels with reference to that of a bare plate immersed in mean flow. Systematic parametric studies are conducted to evaluate the effects of external mean flow speed, noise incident angle and periodical spacings on the aeroelastic-acoustic performance of the rib-stiffened plate.