实际大气中平面波声场的计算
CALCULATIONS FOR THE FIELD OF PLANE SOUND WAVES IN A REALISTIC ATMOSPHERE
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摘要: 本文应用先前工作中关于运动分层介质中平面波反射和折射的一般理论,来解决实际大气中声场的问题。提出计算存在温度梯度和风梯度的多层大气中声场的解析法和图解法。前者给出声场WKB近似及其各次修正项的级数表达式,后者给出直观的图象表示。这些结果具有明晰的物理意义,并且在大多数情形下都可以通过简单的计算得到具体结果,同时也可以作为进一步进行数值计算的基础,这比用直接的数值法求解要简捷得多。Abstract: In this paper, the general theoretic results concerning the reflection and refraction of plane sound waves in a moving stratified medium obtained in a previous work1 have been applied to calculate the sound field in a realistic atmosphere. Two distinct approaches, the analytic one and the graphic one, have been suggested to estimate the sound field in a multi-layered atmosphere where the gradients of both temperature and wind velocity are present. The analytic method gives series expressions for the WKB approximation of the field as well as the successive modifications to it. All these expressions may be used as a basis for obtaining the specific results by some further elementary calculations devoted to the profiles of the realistic atmosphere model. The graphic method gives a clear illustration of the field in a specific example which can be considered as a standard atmosphere. Both approaches enable us to simplify the calculations referred to the usual multi-layer approaches considerably.