The trichromatic mask single-color camera 3D PIV technology uses an optical trichromatic mask element to modulate the imaging light path of a color camera, combining color information with perspective information. This enables the RGB channels of the color-sensitive chip to record images of tracer particles from three perspectives, achieving single-camera 3D flow field measurements. Color cameras typically use a single sensor with a Bayer mask to capture color images. To obtain complete three-channel information of tracer particles, the missing color components in the Bayer image must be restored through demosaicing to extract the three-perspective images. This paper employs High Quality Linear Interpolation (HQLI) algorithms, Gradient Based Threshold Free (GBTF) algorithms, and deep learning algorithms based on U-Net++ neural networks to demosaic particle Bayer images. The quality of three-perspective image extraction by these three algorithms is evaluated using image evaluation metrics and the impact on particle reconstruction quality Q. Simulation experiments on artificially synthesized Gaussian vortex 3D flow fields are conducted to analyze the impact of these algorithms on measurement error. Zero-Net Mass Flux (ZNMF) jet experiments are utilized to study the demosaicing of experimental particle images and analyze the results of transient velocity fields. The results demonstrate that, compared to traditional algorithms (HQLI, GBTF), the deep learning algorithm based on U-Net++ neural networks can more effectively extract three-perspective images of particles, thereby reducing measurement error.

Viscous drag is one of the main sources of civil aircraft drag, and turbulent drag plays a dominant role in viscous drag, so it is of great engineering and scientific significance to carry out turbulence drag reduction control. In this paper, under the condition of a zero pressure gradient experiment, the drag reduction control of the plate boundary layer with isotropic permeating materials fused with micro-blowing is studied. The results show that the isotropic permeable material can significantly reduce the friction drag of the plate surface, and the maximum local drag reduction rate in this paper can reach 55.4%. In addition, compared with the control of a single isotropic permeable material, the isotropic permeating material integrated with micro-blowing not only improves the drag reduction rate in the local region but also increases the flow area of the downstream drag reduction region due to the “memory" of the influence of micro-blowing on the turbulent structure, improving the efficiency of drag reduction. Hot-wire velocity measurement results show that the isotropic permeable material with microblowing can reduce the velocity gradient of the viscous bottom layer of the boundary layer and reduce the momentum exchange between the inner and outer layers. The flow visualization technology of Time-Resolved Particle Image Velocimetry (TR−PIV) showed that the isotropic permeable material integrated with micro-blowing could increase the thickness of the turbulent boundary layer and the pulsation intensity of the flow direction. At the same time, the large-scale high-speed strip structure in the steam-wise direction break down into small-scale structure. The self-holding process and sweeping process near the wall are suppressed, thus achieving drag reduction.

To address the need for measuring soot concentration distributions in complex and spatially constrained combustion flow fields, such as the outlet of aero-engine combustors, this study developed the Two-color-Scheimpflug Laser-Induced Incandescence (2C-Scheimpflug LII) technique and a corresponding measurement system, which obtains soot volume fraction distribution images by employing an oblique imaging method. The technique and measurement system validation experiments were first conducted under specific conditions using three typical ethylene/air flames (McKenna, Gülder, and Santoro). Comparisons with measurement results obtained by other researchers under the same conditions demonstrate the feasibility of the 2C-Scheimpflug LII system. The test results in standard flames show that the lower detection limit of soot volume fraction measurements of our system is approximately 2.0 × 10⁻⁹. Further, the 2C-Scheimpflug LII technique was applied to measure the spatial distribution of soot volume fractions at the transverse cross-section of the outlet and the longitudinal section of a single-sector, dual-swirler aero-engine model combustor. The preliminary results show that the soot volume fraction distribution at the combustor outlet exhibits high instantaneous variability and randomness, while within the combustor, the soot volume fraction displays a V-shaped distribution.