# Particle Image Velocimetry (PIV) measurement data for backward facing step flows with and without periodic perturbations

## Description

Flow fields downstream of a backward facing step with a Reynolds number (UH/\nu) of 9630 were measured using a 2D2C PIV system. Freestream velocity is U=5.7m/s, H=0.025m. Flow was also perturbed using a synthetic jet actuator deployed at the separation point with a range of perturbation frequencies (St= 0.04 to 0.39) and amplitudes (u_A/U= 0.3 to 0.9) . A total of 2000 image pairs were acquired at a rate of 50 Hz for the unperturbed flow, 47 Hz for the flow perturbed at 70 Hz and 49 Hz for other perturbed flow. In this data set, there are a total of 37 data files saved in Matlab2013 MAT format. Files with a name 'f(a)c(b)Vec1.mat' have a size of 3280(spatial locations)*2000(number of snapshots)*2(two velocity components). Unit is m/s. Here in the file name, a=[0:1:9], 0:unperturbed flow, 1:perturbed at 10Hz, 2:20Hz, 3:30Hz, 4:40Hz, 5:50Hz, 6:60Hz, 7:70Hz, 7:70Hz, 8:80Hz, 9:90Hz; corresponding to St=fH/U=[0 0.0439 0.0877 0.1316 0.1754 0.2193 0.2632 0.3070 0.3509 0.3947]; b=[1:1:4], corresponding to perturbation amplitude of u_A/U=[0.3 0.5 0.7 0.9]. The file 'X.mat' and 'Y.mat' is the streamwise and vertical position respectively. Both files have a size of 3280 and normalized using step height, H. More details about the experiment were described in Li, Z.Y., Guo, S., Bai, H.L. & Gao, N. 2019 Combined flow and heat transfer measurements of backward facing step flows under periodic perturbation. Int J Heat Mass Trans 130, 240–251, 10.1016/j.ijheatmasstransfer.2018.10.077. I am available at gaonan@dlut.edu.cn, or a permanent email gaonum@126.com