openpiv.process.extended_search_area_piv

process.extended_search_area_piv()

The implementation of the one-step direct correlation with different size of the interrogation window and the search area. The increased size of the search areas cope with the problem of loss of pairs due to in-plane motion, allowing for a smaller interrogation window size, without increasing the number of outlier vectors.

See:

Particle-Imaging Techniques for Experimental Fluid Mechanics

Annual Review of Fluid Mechanics Vol. 23: 261-304 (Volume publication date January 1991) DOI: 10.1146/annurev.fl.23.010191.001401

Parameters :

frame_a : 2d np.ndarray

an two dimensions array of integers containing grey levels of the first frame.

frame_b : 2d np.ndarray

an two dimensions array of integers containing grey levels of the second frame.

window_size : int

the size of the (square) interrogation window.

overlap : int

the number of pixels by which two adjacent windows overlap.

dt : float

the time delay separating the two frames.

search_area_size : int

the size of the (square) interrogation window from the second frame

nfftx : int

the size of the 2D FFT in x-direction, [default: 2 x search_area_size is recommended].

nffty : int

the size of the 2D FFT in y-direction, [default: 2 x search_area_size is recommended].

Returns :

u : 2d np.ndarray

a two dimensional array containing the u velocity component, in pixels/seconds.

v : 2d np.ndarray

a two dimensional array containing the v velocity component, in pixels/seconds.

sig2noise : 2d np.ndarray

a two dimensional array containing the signal to noise ratio from the cross correlation function.

Examples

>>> u, v, sn = openpiv.lib.extended_search_area_piv( frame_a, frame_b, window_size=16, overlap=8, search_area_size=48, dt=0.1)