In order to improve the measurement accuracy and efficiency of sonic nozzles (SNs) in laminar boundary layer, a correlation model for theoretical discharge coefficient of sonic nozzle taking into account the viscous effects on the boundary layer along the nozzle wall (C_d,th,1), and the multi-dimensional characteristic effect of the core region (C_d,th,2) was proposed. The theoretical discharge coefficient is related to the measurement of geometric parameters, such as the throat diameter, d, and curvature radius, R_c. The detailed geometric measurements of sonic nozzle by 3D coordinate measuring machine were conducted. Then, the evaluation procedures of parameters d and R_c including roundness and waviness profile for designed SNs of d = 7.453 mm and d = 1.919 mm were presented in detail. The effect of waviness profile on the discharge coefficient and boundary layer transient was investigated. It indicated that waviness effect is quite complex. Finally, the validation of the theoretical calculation model of discharge coefficient was verified by the experimental data of National Institute of Metrology (NIM) and National Metrology Institute of Japan (NMIJ) based on the accurate measurements of the geometric parameters. The result showed that the consistency between the C_d,exp and the C_d,th is better than 0.11% when the effect of the heat transfer was considered within the range of Re= (7.33 × 10⁴–1.26 × 10⁶).

为了提高层流边界层中声波喷嘴（SN）的测量精度和效率，考虑了沿喷嘴壁（C _{d，th， 1}），并提出了核心区域（C _d，th，2）的多维特征效应。理论排放系数与几何参数的测量有关，例如喉径d和曲率半径R _c。通过3D坐标测量机对声波喷嘴进行了详细的几何测量。然后，参数d和的评估程序 详细介绍了d  = 7.453 mm和d = 1.919 mm的设计SN的包括圆度和波纹度轮廓的R _c。研究了波纹度分布对放电系数和边界层瞬变的影响。这表明波纹效应是相当复杂的。最后，在精确测量几何参数的基础上，通过国立计量研究所（NIM）和日本国立计量研究所（NMIJ）的实验数据验证了排放系数理论计算模型的有效性。结果表明，C _d，exp和C _d，th之间的一致性当在Re =（7.33×10 ⁴ –1.26×10 ⁶）的范围内考虑传热效果时，该值优于0.11％。