3D3C rainbow particle tracking velocimetry: improving depth resolution and velocity vector acquisition rate by using color space for a multi-cycle rainbow pattern

Rainbow particle tracking velocimetry can be used to measure 3D3C flow velocity vectors with a single color camera. The particle depth position is calculated from the hue degree of a particle color. A liquid–crystal display (LCD) projector can be used conveniently as a light source of the color pattern in place of the spectral diffraction of white light. Another advantage of using an LCD projector is the ability to change the RGB components of the color pattern. In this study, the rainbow color pattern was modified to increase available color. Colors with the same hue degree but different saturations were used in the color pattern. Using color space enhanced positional resolution in the color change direction. The parameters of new color patterns were number of cycles, saturation continuity and range of color space. They were designed and their performances were compared. The effective resolution in color change direction enhanced 2.4 times from original patten (single cycle rainbow), and velocity vector acquisition rate improved, in particular, for the range of small amount movement per step.

Graphical abstract