小瓣数贝塞尔声束的二次谐波
Second-harmonic generation of the Bessel sound beam of several lobes
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摘要: 采用高斯展开法,研究了具有三个瓣的小瓣数贝塞尔声束的基波和二次谐波的传播性质.根据准线性近似下Khokhlov-Zabolotskaya-Kuznetsov方程的积分形式解,分析了媒质的声吸收(声衰减)对波束形状的影响.结果表明:吸收参量对二次谐波径向分布有很大的影响.当瓣数较少时,实际的有限孔径贝塞尔声束二次谐波仍然具有理想无限大孔径贝塞尔声束的主要特征,在近场无衍射区,径向几乎无衍射.Abstract: By the Gaussian expansion approach we investigate fundamental-and second-harmonic generation in practical Bessel beams of several lobes.The analysis is based on the integral solutions of the Khokhlov-Zabolotskaya-Kuznetsov equation under the quasilinear approximation.The influence of the medium attenuation on beam profile is considered.Numerical results show that the absorption parameter has a significant effect on the beam profile of the second harmonic.Under certain circumstances,the second harmonic of a practical Bessel beam with several lobes still has the main properties of an ideal Bessel beam of infinite aperture when it propagates within its depth of field.
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