Abstract:

An experimental study on the effect of stream turbulence on some measuring methods of boundary layer transition has been conducted, and indicates that the method to measure rms level of random signal is more effective for detecting boundary leyer transition, because in the transition process, the difference of the rms level of random signal is larger and stable. Mean while, in this paper, the effect of stream turbulence and inputing noise with different fregqency of the rms value distribution of velocity fluctuation in the transition region has been studied, and indicates that there is max. rms value of the fluctuation and it is located near 0.2(5 high, in spite of existing the turbulence and noise. Finally, it is suggested that the criterion of indicating the beginning and ending point of transition region must be studied further for the precision of transition region measurement.

Key words: Boundary layer, Boundary layer transition, Measurement