The two-dimensional velocity shift caused by the use of a rotating mirror in PIV flow field measurements

A theoretical analysis of the two-dimensional velocity shift by the use of a rotating mirror in PIV flow field measurements has been carried out by the application of ray optics. The velocity shift has been calculated directly in the flow field co-ordinates. In dimensionless form the results are also available in the image plane. It is shown that the distribution of the velocity shift over the entire observation field may not usually be assumed to be uniform (and may vary by up to 20%). The effect of the layout and arrangement of the rotating mirror on the velocity shift and its distribution has been analysed. In addition, the sensitivity of the velocity shift to the design tolerances and imperfections of the rotating mirror is given.