A Method of Discriminating Flow State in Flight Test Based on Friction Variation Law

Abstract

The invention discloses a flight test flow state distinguishing method based on friction resistance change rules. The method comprises the following steps: (1) calculating the axial force coefficientCA_identification of an aircraft corresponding to each flight moment in the whole flight process of the aircraft by adopting an aerodynamic identification method; (2) calculating the wave resistance Cap_calculation corresponding to each flight moment in the whole flight process of the aircraft according to an aerodynamic data table of the aircraft; (3) performing subtraction on the axial force coefficient CA_identification of the aircraft corresponding to each flight moment in the whole flight process of the aircraft and the wave resistance Cap_calculation, so as to obtain a friction resistance Caf_identification changing curve for the whole flight process of the aircraft; (4) dividing a friction resistance curve into two sections by taking the minimum point in the friction resistance curve as a boundary, dividing each section of the friction resistance curve into a plurality of sub-intervals, and calculating the friction resistance variation delta Caf_identification in each sub-interval; and (5) finding out the biggest influence factor of the delta Caf_identification, and if the flow state change causes the dominance of the friction resistance variation delta Caf_tran to the deltaCaf_identification, judging that the surface flow state of the aircraft changes so that transition from laminar flow to turbulent flow occurs.

Description

technical field [0001] The invention relates to a flight test fluid state discrimination method based on frictional resistance variation law, which belongs to the field of aircraft aerodynamic characteristic design. Background technique [0002] The transition of the flow state on the surface of the aircraft will have a significant impact on the aerodynamic characteristics of the aircraft. The transition leads to obvious changes in friction, heat flow, and surface temperature rise. As the transition front advances, changes in the aerodynamic characteristics of the aircraft will cause changes in the trim rudder deviation. [0003] In order to analyze the influence of the change of the flow state on the surface of the aircraft on the aerodynamic characteristics, it is necessary to judge whether the flow state on the surface of the aircraft changes. In the flight test, the transition process and transition front information are obtained by arranging heat flow sensors and tempe...

AI Technical Summary

Problems solved by technology

This method can give information such as whether the feature position is in transition, the height at which the transition occurs, and the Mach number, etc., but this kind of refined research requires a large number of sensors

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