Numerical Simulation Of Active Control Of Underwater Acoustic Radiation Of Structure Containing Piezoelectric Patches

It is a hotspot in the current research that the appliance of intelligent structures in the fields of structures vibration and yawp control. Intelligent structures have been used in the big space structures require high capability to adapt its environment. Active control of underwater structural acoustic radiation is very important for achieving quiet structures. First the design procedures such as simulation-based-design and vibration-and-noise-control-by-design for achieving a quiet submerged structure are based on the numerical analysis of response behavior of the submerged structure. Second active structural acoustic control has emerged as a very promising method to reduce structural radiated noise at low frequencies. The piezoelectric materials have been widely used in the field of structural yawp active control as a new type of smart materials because of their excellent mechanical-electrical coupling characteristics.In the beginning of this thesis, types and characteristics of piezoelectric material elements have been introduced. And the basic equations of piezoelectric material have been given, the appliance of piezoelectric material in the field of structural acoustic radiation active control. After that coupling the boundary element method which is based on the surface integral equation of pressure in mean flow with structural finite element method to obtain motion equation of fluid-structure interaction. Then piezoelectric structure is derived by using Hamilton's principle. A finite element formulation of a plate integrated with piezoelectric patches is developed on the basis of the electroelastic behavior using the Mindlin plate theory, and respondent and active equations are given. According to the mechanical-electrical coupling characteristics of piezoelectric materials, the frequency-response function related to active voltage and displace of a beam is gained, from which it is known the best position for actuator is where the stain is the biggest. After then, boundary element formulation based on the Rayleigh integral in the plate surface is coupled with the derived finite element formulation to model acoustic fluid-structure interaction of a structure with piezoelectric patches. In the end, the effect of active control of air and underwater acoustic radiation through changing the action place and gain are discussed, from which it is gotten in air the best position for actuator is where the stain is the biggest, but is not the very some in water. Then by discussing the relationship between active voltage and control gain, it is known adjusting the gain can improve the effect of active control, but it must make sure the active voltage can not beyond the max working voltage of pzt. And...