Based upon the thermodynamics analysis of fluid flowing near critical region, this paper attempts to describe the flow characteristics of compressible fluid by using isentropic compressibility Ks instead of the ratio of specific heats y. 本文基于对流体在近临界区流动的热力学分析,试图用等熵压缩度Ks代替比热比γ来描述可压缩流体通过文丘里管的流动特性。