Visualization and Measurement of Indoor Airflow by Color Sequence Enhanced Particle Streak Velocimetry

Abstract

Airflow measurement plays a crucially important role for studying the indoor environment. Two primary nonintrusive airflow approaches that use bubbles as seeds to visualize and track the airflow are particle tracking velocimetry (PTV) and particle streak velocimetry (PSV). The major advantage of PTV and PSV is the limited disturbance they impart to the tested airflow. However, the drawback is that they are not capable of room-scale measurements. Therefore, a new approach, i.e., color sequence enhanced particle streak velocimetry (CSPSV), is introduced. The core component of CSPSV is the color sequence illumination system (CSIS), which consists of three controlled lights of different colors and one of white light. The concept is to change the illumination color of the test zone in a given sequence during the exposure time. Then the color-coded time sequence information is inputted into an algorithm for both three-dimensional (3D) reconstruction and stereo pair matching. The theory and composition, image-processing and pair-matching algorithms, verification and applications of CSPSV are introduced in the chapter. The relative magnitude error of CSPSV is mostly below 5% within 0.12 ~ 2.45 m/s, and the results from CSPSV are in consist with a hot-wire anemometer. CSPSV can be used in different indoor airflows such as vortex flow, airflows induced by the ceiling fan and adjustable fan networks, etc. CSPSV combines the advantages of PTV and PSV, reduces the requirement for high-speed cameras, and can be easily extended to measure the airflow in a large space.KeywordsNonintrusive measurementParticle streak velocimetryIndoor airflowDigital image processColor sequence illumination