Chapter3 Integral Relations(积分关系式) for a control volume in One-dimensional steady Flows 31 Systems(体系) versus Control volumes(控制体) System: an arbitrary quantity of mass of fixed identity. Everything external to this system is denoted by the term surroundings, and the system is separated from ts surroundings by it's boundaries through which no mass across.( Lagrange拉格朗日) Control Volume(Cv: In the neighborhood of our product the fluid forms the environment whose effect on our product we wish to know. This specific region is called control volume, with open boundaries through which mass momentum and energy are allowed to across (Euler Efi) Fixed Cv, moving Cv, deforming Cv3.1 Systems (体系) versus Control Volumes (控制体) System：an arbitrary quantity of mass of fixed identity. Everything external to this system is denoted by the term surroundings, and the system is separated from its surroundings by it‘s boundaries through which no mass across. (Lagrange 拉格朗日) Chapter 3 Integral Relations（积分关系式） for a Control Volume in One-dimensional Steady Flows Control Volume (CV): In the neighborhood of our product the fluid forms the environment whose effect on our product we wish to know. This specific region is called control volume, with open boundaries through which mass, momentum and energy are allowed to across. (Euler 欧拉) Fixed CV, moving CV, deforming CV