外表面应力自由的充液有限壁厚井孔中的声场及其频散曲线的“平台”特征  

Wavefield in a fluid-filled cylindrical shell with outside traction-free boundary conditions and its "plateau" characteristics in dispersion curves

作　　者：王晶[1] 陈德华[1] 张海澜[1] 王秀明[1] 

机构地区：[1]中国科学院声学研究所声场声信息国家重点实验室,北京100190

出　　处：《声学学报》2012年第3期232-236,共5页Acta Acustica

基　　金：国家自然科学基金(40774099;10874202;11134011);国家高技术研究发展计划(863)(2008AA062205)

摘　　要：为了开发一种新型标准刻度井,对外表面应力自由的充液有限壁厚井孔中的声场进行了更加深入的研究,计算分析了这种圆柱形封闭声波导结构中的声场和多阶对称模式波的频散特性。结果表明:充液有限壁厚井孔中高阶对称模式波的相速度频散曲线在一定频率范围内出现"平台"现象;当声源激发主频大于5 kHz且慢度时间相关法(STC)的窗长取4到5个周期时,得到全波波形中的"首波"速度与高阶模式波相速度频散曲线上的"平台"区域速度接近,该"平台"区域的速度与有限壁厚管材的纵波速度相差百分比随管材泊松比增加呈指数型上升;通过选择合适的管材材料以及改变其几何尺寸,可在一定频率范围内控制对称模式波相速度频散曲线的"平台"宽度、位置及平稳度。这一研究可为建立行业标准的声速刻度井提供新思路。In order to develop a kind of standard calibration borehole,studies on acoustic wavefield in a fluid-filled borehole with outside traction-free cylindrical boundary conditions are intensified.Dispersive characteristics of various symmetric mode waves in this kind of cvlindrically closed waveguide structure are calculated and analyzed.Numerical results show that,the dispersion curves of the fluid-filled borehole go across between the dispersion curves of the empty borehole and the fluid cylinder.The so called head velocities calculated by the Slowness-Time-Coherence（STC） method have a great agreement with the values in the ＂plateau＂ range on the phase velocity dispersions curves.When the window length is 4 to 5 times of the wave cycles,the difference between the ＂plateau＂ velocity and the longitudinal velocity of the borehole material increases exponentially with the incensement of the Poisson＇s ratio of the borehole material.It is also shown that the size of the borehole radius could be chosen for obtaining the appropriate plateau width,location and smoothness.This work may provide a new sight for designing borehole acoustic logging calibrations.

关 键 词：频散曲线 表面应力 平台 壁厚 声场 井孔 充液 自由 

分 类 号：O422.2[理学—声学]