2 Experimental results and analysis
The instantaneous velocity vector field
data were averaged over time, and the mean square of the flow velocity
and normal pulsation velocity were obtained. The flow pulsation
intensity and normal pulsation intensity were as follows:
In the formulas, and indicate the fluctuation intensity of the flow and
normal pulsation intensities, respectively; and represent the flow
instantaneous velocity and normal instantaneous velocity at a certain
position (x.y) at a certain time t, respectively, that are acquired by
PIV in the flow field; N is the period of PIV acquisition; and C is the
number of acquisitions in the PIV field of view.