管道流中非线性行波的实验观察检测方案(粒子图像测速)

With stereoscopic particle image velocimetry (SPIV) we can measure all 3 components (3C) of the velocity in the plane of a laser light sheet. SPIV makes use of 2 cameras that view the laser light sheet from two different directions. In each measurement point in the plane of the light sheet, each camera measures the projection of the particle displacement perpendicular to its viewing direction, and the complete velocity vector can be reconstructed from these projections. First the 2C-vector fields from each camea must be mapped (dewarped) from the image planes onto the measurement plane of the light sheet and interpolated on a common grid. Then the displacement vectors from both cameras are combined to calculate (reconstruct) the 3 components of the particle displacement. The dewarping and reconstruction can in principle be based on the exact knowledge of the geometry of the setup, but most often they are based on a calibration procedure. The geometry of the setup is then derived from a set of calibration images from a grid placed in the measurement plane. A more extensive discussion of the dewarping, the reconstruction and the 3D-calibration procedure is given in (S1-S6).