Figure 1
Block diagram for the hybrid method.
Table 1
Inputs.
| INPUT FILES AND PARAMETERS | NOTATION | UNIT | NOTE |
|---|---|---|---|
| image pair | Im1, Im2 | – | tif, bmp, jpeg etc. |
| Lagrange multipliers | lambda_1 for the Horn-Schunck estimator lambda_2 for the Liu-Shen estimator | – | regularization parameter in variational solution |
| Gaussian filter size | size_filter | pixel | removing random image noise |
| Gaussian filter size | size_average | pixel | correction for local illumination intensity change |
| scale factor for downsampling of original images | scale_im | – | reduction of initial image size in coarse-to-fine scheme |
| number of iterations | no_iteration | – | iteration in coarse-to-fine scheme (≥ 1) |
| left and upper edge width | edge_width | pixel | clean left and upper edges where abnormal data may occur |
| indicator for regional diagnostics (0 or 1) | index_region | – | “0” for whole image; “1” for selected region |
| sizes of interrogation area | pivPar.iaSizeX | pixel | defining multi-path of windows |
| grid spacing | pivPar.iaStepX | pixel | defining overlapping |
| method for calculating cross-correlation | pivPar.ccMethod | such as ‘fft’ |
Table 2
Outputs.
| OUTPUT FILES | NOTATION | UNIT | NOTE |
|---|---|---|---|
| coarse-grained velocity | ux0, uy0 | pixels/unit-time | based on downsampled images |
| refined velocity | ux_corr, uy_corr | pixels/unit-time | refined result with full spatial resolution in coarse-to-fine process |
Figure 2
A pair of particle images of an Oseen vortex pair in a uniform flow, (a) Image #1, and (b) Image #2.
Figure 3
Flow fields of an Oseen vortex pair in a uniform flow extracted from the particle images, (a) velocity vectors, (b) velocity magnitude, (c) vorticity, and (d) second invariant (Q).
Figure 4
A pair of particle images of vortex-induced separation in a wall-jet region of a normally impinging jet, (a) Image #1, and (b) Image #2.
Figure 5
Flow fields of vortex-induced separation in a wall-jet region of a normally impinging jet extracted from the particle images, (a) velocity vectors, (b) velocity magnitude, (c) vorticity, and (d) second invariant (Q).
Figure 6
A pair of particle images of acoustically excited twin jet, (a) Image #1, and (b) Image #2.
Figure 7
Flow fields of acoustically excited twin jet extracted from the particle images, (a) velocity vectors, (b) velocity magnitude, (c) vorticity, and (d) second invariant (Q).