To improve the accuracy of the wind tunnel test, relying on the high-pressure gas source of the China Aerodynamic Research and Development Center, a secondary flow standard facility based on a sonic nozzle array was developed, with a pressure range of (1~6) MPa and a flow range of (0.12~5.55) kg/s. Currently, most facilities use the average temperature measured by the temperature array to represent the upstream temperature of the sonic nozzle array. However, the small flow calibration test results showed that the maximum temperature difference upstream of the standard sonic nozzle array was 1.97 K, and the temperature field upstream of the sonic nozzle array showed non-uniformity, so the above method cannot accurately obtain the upstream temperature. To solve this problem, each nozzle used in the standard sonic nozzle array was accurately measured by temperature sensors. The uncertainty of the facility and the discharge coefficient of the calibrated nozzle between the two methods were compared. The results showed that compared with the discharge coefficient obtained using the temperature sensor array of 0.9902, the accurate measurement of 0.9904 was closer to the National Institute of Metrology, China (NIM) traceable result of 0.9907, and the relative uncertainty of the facility was reduced from 0.124% (k = 2) to 0.120% (k = 2).

The flow structure and unsteady evolution characteristics of dual impinging jets represent a flow problem of significant engineering importance in the aerospace field. Currently, there is a lack of systematic research on the unsteady characteristics and the underlying mechanisms of flow structure evolution in dual impinging jets across different velocity regimes. This study investigates a dual impinging jet configuration with a nozzle pressure ratio ranging from 1.52 to 2.77, an impingement spacing of 5d (where d is the nozzle exit diameter), and an inter-nozzle spacing of 10.42d. By employing Particle Image Velocimetry and Proper Orthogonal Decomposition, the evolution of the flow field structure from subsonic to supersonic conditions is systematically analyzed. The results demonstrate that the fountain motion is composed of an anti-symmetric oscillatory mode, a symmetric breathing mode, and an intermittent transport mode. The upper confinement plate obstructs the fountain motion to some extent, inducing unsteady oscillation modes. An increase in jet velocity enhances the upwash momentum of the fountain and raises the characteristic frequencies of its dynamic structures. This research elucidates the influence of jet velocity variation on the flow field structure, providing a theoretical basis for formulating flow control strategies in related engineering applications.

In order to improve the accuracy of wind tunnel test, relying on the high pressure gas source of China Aerodynamic Research and Development Center, a secondary flow standard facility based on sonic nozzle array is developed, and its pressure range is (1~6)MPa, and flow range is (0.12~5.55)kg/s. At present, most facilities use the average temperature measured by the temperature array to represent the upstream temperature of the sonic nozzle array. However, the small flow calibration test results show that, the maximum temperature difference upstream of the standard sonic nozzle array is 1.97 K, the temperature field upstream of the sonic nozzle array shows non-uniformity, so the above method cannot accurately obtain the upstream temperature. To solve this problem, each nozzle used in the standard sonic nozzle array was accurately measured by temperature sensors. And the uncertainty of the facility and the discharge coefficient of the calibrated nozzle between the two methods were compared. Results show that, compared with the discharge coefficient obtained by the tempearture sensor array of 0.9902, the accurate measurement of 0.9904 is closer to National Institute of Metrology, China(NIM) traceable result of 0.9907, and the relative uncertainty of the facility is reduced from 0.124% (k=2) to 0.120% (k=2).