Separation detection with stochastic signals from flush-mounted hot-film sensors

The location of boundary layer separation and reattachment is carried out with an array of hot-film sensors. The test geometry is a low speed boundary layer in a circular tube that separates at a step-wise expansion in the tube diameter. The phase relationship between sensor signals (in- phase or out-of-phase) is used as the locating tool. The unique aspect of the study is determining the phase relationship with time-domain analysis of the cross correlation of simultaneous sensor signals. This technique is appropriate for the stochastic (random) signals present in the test geometry, and this technique gives results even when the phase relationship in the data is not observable by eye.