中文摘要：

三个互相联合的基本过程(砍，压缩，并且热)在一般液体运动，仅仅为压缩过程的一般明确的表达和它的子进程， aeroacoustics 的题目，以及他们砍的物理结合和热过程，到目前为止没到达一致。这种状况为各种各样的深入的复杂 multiprocess 流动诊断，最佳的配置设计，和流动 / 噪音控制引起了困难。作为向在充分非线性的政体的需要的明确的表达的第一步，这份报纸采用操作符因式分解方法重游基本进程和他们的分解的分析线性理论，特别压缩进程进的进一步的切开声学并且熵模式，在 1940 年代鈥 ? 980s 发展了。这里对待的流动是在与质量，外部身体力量，和热增加的任意的来源一起的一个无界的领域的可压缩、粘滞、进行热的多花采蜜的气体的小骚乱。以前的结果从而被修订并且延长到一个完全、统一的理论。理论为由澄清某些基本问题开发相应非线性的理论提供一个必要基础和珍贵指导，例如压缩进程和他们的管理方程的特征的典型变量的合适的选择。关键词纵(压缩) 进程 - 横过(砍) 进程 - 声学的模式 - 熵模式 - Aeroacoustics 工程被中国(2009CB724100 ) 的国家基本研究程序支持。

英文摘要：

Of the three mutually coupled fundamental processes （shearing, compressing, and thermal） in a general fluid motion, only the general formulation for the compress- ing process and a subprocess of it, the subject of aeroacous- tics, as well as their physical coupling with shearing and thermal processes, have so far not reached a consensus. This situation has caused difficulties for various in-depth complex multiprocess flow diagnosis, optimal configuration design, and flow/noise control. As the first step toward the desired formulation in fully nonlinear regime, this paper employs the operator factorization method to revisit the analytic linear theories of the fundamental processes and their decomposi- tion, especially the further splitting of compressing process into acoustic and entropy modes, developed in 1940s-1980s. The flow treated here is small disturbances of a compressible, viscous, and heat-conducting polytropic gas in an unbounded domain with arbitrary source of mass, external body force, and heat addition. Previous results are thereby revised and extended to a complete and unified theory. The theory pro- vides a necessary basis and valuable guidance for developing corresponding nonlinear theory by clarifying certain basic issues, such as the proper choice of characteristic variables of compressing process and the feature of their governing equations.