Research Of Real-time Measurement System And Problems In Compressible Flow Measurement For Seven-Hole Probes

Flow measurement is an important way to study the aerodynamic character of an aircraft. Seven-Hole Probe (SHP) as a tool of flow measurements has many special advantages in measuring. Now, many researches are limited in incompressible flows at domestic and there isn't any immediate measure system for seven-hole probe which cause the calibration and measurement process complicated. In the present research, in connection with SHP, a real time measurement system and a method for compressible flow are studied based on the software of Labview and computational fluid dynamics.Composed by Labview and high accuracy pressure transmitter and data acquisition card, the SHP test system not only has a nice operation contact surface and simplified the measuring process but also stratified the real time measurement demand with excellence stability and accuracy when worked on a helicopter bottom.In this paper, the flow fields of SHP are studied by numerical simulation. Pressure distributions, path line, and velocity vector on the tip of SHP are given. The differences of separation area are compared between Mach number 0.6 and 1.0. The result show that flow begins to separate whose form is opening as the angle of attack is up to 30 degree and the area grow more with the angle increased; when below high angle of attack, flow separation become more and more along the probe axis and the scope are difference in vary Mach number.The calibration and measurement method in compressible flow are studied by the data from numerical simulation. The accuracy of calibration fitting of flow angle is about 2%, and the relative value of both the total pressure and static pressure are less than 3%. This result is better than the experiments in same situation. Finally, the flow measurement with SHP in non-isentropic unknown supersonic field is discussed. Moreover, pressures received by SHP tube added with temperatures which are monitored around the border between cone and cylinder is the key to judge the flow is supersonic or not.