Research Of Wind Tunnel Experiment Measurement For Seven-Hole Probles

As a kind of pneumatic measuring devices,the seven-hole probe can at the same time obtain the size of the flow velocity, direction, and the total pressure and static pressure, and it is widely used for testing a variety of wide-angle measurement of the flow in low-speed wind tunnel.Seven-hole probe measurements are of high precision, simple equipment,low price and lowly requestment on the environment. It has broad prospects in measurement of the flow field.In this paper, seven-hole probe testing system for the distribution in low speed wind tunnel at the Nanjing University of Science and technology for the first time was established. A good platform was established for carrying out flow distribution testing.The main research contents were included as follows:Firstly, the structure, working principle and several common calibration method of the seven-hole probe were discussed in detail. The foundation for designment of seven-hole probe testing system were accomplished.Secondly, according to the actual situation in the low speed wind tunnel laboratory a seven-hole probe testing system was designed independently,and the hardware components were mainly included by the shift coordinate frame, pressure sensors, signal amplifiers and data acquisition card form. Meantime according to the characteristics of data collection, a reasonable data-processing method was designed and the processing softwares were developed.Thirdly, the applications of the seven-hole probe in the low-speed incompressible flow field measurement applications were studied. NACA6321 airfoil and a missile body were carried out a series of flowing measurment experiments. The airfoil in a certain wind speed, the different angle of attack, the test section around an airfoil at different locations and the projectile velocity vector of the backward-facing step flow, static pressure and other flow field parameters were studied.Fourthly, in order to further validate the measured results, NACA6321 airfoil were numerical simulated. Through theoretical analysis, experiments and numerical comparison, good agreement between experiment and calculation, and the measured velocity vectors, static pressure and other parameters of flow field around the airfoil flow field consistent with the basic law, which verifies the reliability of the test system were shown.Fifthly, the interference with presence of poles and seven-hole probes to theory flow of experimental model experimental probes was analysed quantitatively. Five sets of three-dimensional computational model was established, which include a photo-elastic body, four models of typical experimental point position with probes. The static pressure, velocity and other flow field parameters were compared of the five models. The results of the projectile flow field were analyzed with or without probes.The credibility of measurement of low-speed flow field with seven-hole probe was analyzed and the disturbance extent of probe and strut was determined.Thus foundation for the data credibility of seven-hole probe used in low-speed wind tunnel flow field measurement was laid.