Abstract: The numerical models of the water-filled pipe systems baffled with an elastic circular plate are established based on the Finite Element Method(FEM).The influences of the bends on the sound energy radiated from the fluid outlet and the elastic plate are emphatically analyzed for different excitation conditions which include the plane wave and force excitations.The results show that the high-order circumferential modes coupling between the shell and the inner flow resulted from the elbow extremely influences the structure vibration and the fluid sound propagation.Consequently the total radiated sound energy and the dominant sound energy sources of the system are changed,and these vary with the types of excitations and frequencies.For the studied pipe systems under plane wave excitation,the sound energy in the low frequency band is mainly structure radiation,and the high frequency band is characterized by the alternation of fluid sound and structure sound.For the radial force excitation,the sound energy of the straight pipe system is nearly all radiated by the elastic plate,however,the sound power from the nozzle promptly increases once the elbow couples with the fluid.For the axial force excitation,the total radiated sound power of the curved pipe system is significantly decreased,but the sound power at the flow outlet is still increased due to this coupling effect.