| Modern optical flow diagnostics can offer a great potential for providing unprecedented understanding of various complex flows: that is, steady or unsteady, laminar or turbulent, and small- or large-scale, which arise in many engineering applications. Among various flow properties, velocity can be the most important since it can greatly influence other properties through convective interaction. The technology development for providing three-dimensional (3-D) three-component (3-C) velocity diagnostics thus becomes very important in modern engineering. In this effort, stereoscopic tracking velocimetry (STV) has been developed, which can simultaneously track numerous markers (particles or bubbles) in 3-D space.;One of the successful application examples is the entire flow measurement around a large model parachute. By seeding the measurement volume with neutrally-buoyant helium soap bubbles as velocity markers, the flow field can be visualized for quantitative velocity information extraction. The testing can be conducted for a medium-scale model with high-speed high-resolution cameras. The performance of the developed technique is assessed through computer simulation of experiments as well, which can provide the known velocity values of 3-D test fields for technology evaluation. For measuring the large parachute flow with several-thousands particles seeded, special software techniques have been implemented for improving the speed and accuracy in data acquisition and processing. The measurement system also needs incorporation of pertinent advanced hardware. In computer simulation of experiments for the STV evaluation, fluid-structure interaction simulation between ambient air and parachute canopy has been considered in CFD flow calculation for reference data. |
