Abstract

The Harmonic Generation in Bounded Bessel Field

C.Tao, J.Ma, Z.Zhu, G.Du (State Key Lab of Modern Acoustics & Institute of Acoustics, Nanjing University, P.R.China)

e-mail: zhudu@nju.edu.cn

Recent literatures pointed out that the ultrasonic field excited by a boundless Bessel source is a Bessel field and proved using the perturbation method that its n-th harmonic is simply related to Bessel distribution. However, the ultrasonic field excited by a bounded Bessel source is more realistic than the boundless Bessel field, just like the piston field (bounded plane field) versus the plane field. This article discusses the bounded Bessel field using Fourier series expansion and numerical methods to solve the KZK equation. Calculation results show that like the piston field, the bounded Bessel field can be partitioned into the nearfield and the farfield. The nearfield distance of Bessel field is much shorter than that of piston field. And its harmonic obeying Bessel distribution is only limited in the nearfield. This is quite a limited region. In the farfield, the harmonics are far different from Bessel distribution. In addition, the harmonics' distributions of bounded Bessel field in different region are discussed in detail in this article.

Section : 1