Two-axes Scheimpflug focusing for particle image velocimetry
Stephen Walker; Stephen Walker; NASA Ames Research Center, MS 260-1, Moffett Field, CA 94035-1000, USA
Журнал:
Measurement Science and Technology
Дата:
2002-01-01
Аннотация:
The objective of this work is to demonstrate the capabilities of a two-axes, three-dimensional particle image velocimetry (PIV) system for future use as a large-scale wind tunnel research tool. A two-axes PIV system provides the capability for camera placement virtually anywhere within three-dimensional space relative to the laser sheet plane of measurement. The Scheimpflug focusing method is applied in two orthogonal axes to achieve off-axis focusing. The two-axes, three-dimensional PIV system uses off-axis stereoscopic viewing to determine two perspective measurements of a three-dimensional velocity field within the laser sheet. A unique calibration procedure is used to determine the optical parameters that describe the position of the camera systems and which are necessary to perform the three-dimensional reconstruction of the displacements. This paper presents the calibration procedure as well as a method for reconstructing the three-dimensional particle displacements for this two-axes, three-dimensional PIV system. This two-axes, three-dimensional PIV system was demonstrated by measuring three-dimensional displacements of a target. Maximum instantaneous errors are estimated as 2% or less for all velocity components. These error estimates are for instantaneous displacements and include all error sources. The two-axes, three-dimensional PIV system was also used to make measurements of the freestream velocity within a wind tunnel. The out-of-plane freestream component of velocity measured by the PIV system differed from the expected value by less than 1.1{%}.
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