Interrogation region

A detailed investigation of the flow, using PIV, with and without control is carried out. The instantaneous velocity field is obtained by the method described in section 18.2, with interrogation regions of 6 x 6 pixels corresponding to a physical dimension of 0.36 X0.36 mm. Typical mean and instantaneous velocity fields of the near region of a flame without suction at U =3.9 m/s and = 2.0 are shown in Figs. 18.6a and 18.66, respectively. 

X 0.9 jim near the wall was obtained. By overlapping the interrogation regions 50 %, a velocity vector spacing of 450 nm in the wall-normal direction is obtained. 

Most commonly used interrogation region dimensions are 64 x 64 pixels for autocorrelation, and 32 x 32 pixels for cross-correlation analysis. Since the maximum particle displacement is about a third of these dimensions, to achieve reasonable accuracy and dynamic range for PIV measurements, it is necessary to be able to measure the particle displacements with subpixel accuracy. 

The spatial resolution of PIV can be increased using mnltipass correlation approaches. Offsetting the interrogation region by a value equal to the local... 

The in-plane displacement should be limited to 1/4 of the size of the interrogation region. 

The cross-correlation function at a certain interrogation region is represented by... 

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