Abstract:

Modification of active aircraft is an effective and quick approach to endow it with new functions or to raise its performance and fighting capacity. Preventing the structural vibration of the component under modification is a rather difficult technological point. One of the chief arousing sources of the vibration of the component under modification is the fluctuating pressure of the component flow. This paper describes the features of the component flow and its fluctuating pressure, provides an optimum modification design method for the external shape of the component, and presents the main result of a study on the correlation of the wind tunnel experiment and the flight test for the fluctuating pressure of the component flow. The fluctuating pressure in the strong separated flow area behind the bluff component under modification is very high, and the data correlation of wind tunnel experiments with flight tests is highly good. The fluctuating pressure caused by the shock wave at the shoulder of the component under modification is relatively high, and the data correlation of wind tunnel experiments with flight tests is fairly good, and highly good at the low frequency band. On the contrary, the fluctuating pressure in the attached flow area is very low, and the data correlation of wind tunnel experiments with flight tests is poor due to the output signals of wind tunnel experiments concealed by the wind tunnel background noise.

Key words: aircraft modification, fluctuating pressure, wind tunnel experiment, flight test, correlation