The characteristic analysis of phase-controlled array thermo-acoustic emission with multiple emitting surfaces

Thermo-acoustic (TA) ultrasound, particularly when combined with phased-controlled array technology, has garnered significant interest in the past decade due to its numerous advantages. This paper establishes a theoretical expression for thermo-acoustic phased array (TAPA) emission to investigate different acoustic fields based on input heat flow frequencies, quantities and distances of TA emission surfaces, area of emission surfaces, and phase changes between emission surfaces. The study finds that a TAPA with two emitting surfaces in a line pattern produces a consistent acoustic field compared to a single emitting surface arranged in a semicircle. Additionally, applying different phases on the surfaces narrows the scanning range with an increase in frequency, area of the TA emission surface, and the amount of emission surfaces, while enhancing the directivity of the TA wave. Moreover, increasing the distance between emitting surfaces in a square-shaped TAPA does not affect the ultrasound pressure of the main TA ultrasound but increases the quantity and size of side lobes. Furthermore, enlarging the area of emitting surfaces enhances the directivity of the TA ultrasound, necessitating a reduction in the distance between emitting surfaces or an increase in the area of the emitting surfaces in a square-shaped TAPA to enhance directivity. This paper provides a comprehensive study of TAPA to aid further research in this field.