Effects of element number of linear phased array acoustic transmitter on waves of various modes in fluid-filled borehole

Key words:  linear phased array acoustic transmitter  acoustic logging  finite element method  element number of array  steered angle

Abstract:

Effects of the acoustic logging transmitter of linear phased array composed of point source on waves of various modes in fluid-filled borehole were studied by finite element method (FEM). And the influence of element number of array on wave amplitude was mainly analyzed. The results show that the steered angle of acoustic arrays increases with the delay time increasing between the neighbour elements. When the angle of radiated acoustic beam steered to the critical angle of the compressional or shear wave, the amplitude of the compressional or shear wave can increase in direct ratio with the element number of the phased array. If the steered angle of radiated acoustic beam departs from the critical angle of the compressional or shear wave in other controlled delay time, the enhancement of the amplitudes is little. And when the element number is changeless, the amplitude of the ccxnpressional or shear wave can be strengthened gradually with the steered angle increasing. But when the steered angle exceeds the critical angle, the amplitude will be lowered with the steered angle increasing sequentially.