Study On Three-dimensional Reconstruction Of Flame And Two-phase Flows Based On High-speed Stereoscopic Imaging

The front shape of flame is identified as a significant variable influencing fire spread. The spatial information such as three-dimensional (3-D) flame structure would be useful for understanding the mechanism of fire propagation as well as for developing flame dynamics simulations. Although flame structures have been widely visualized photographically no quantitative 3-D data of flame has been reported so far. The inherent three-dimensional nature of the flame surface front is a challenge to present available flame diagnostic techniques.Gas and Solid two-phase flows play a key role in variety of natural and industrial processes. These phase interactions are, in general, three-dimensional and unsteady. Therefore, measurement techniques utilized to obtain qualitative and quantitative data from two-phase flows need to be extended to acquire transient and three-dimensional data.It is an important subject for the turbulent flows research field to analyse the 3-D characteristics of flows using optical technology. The conventional image-capture process involves light integration along the optical path which means a loss of in-depth information. Aiming at the problem of present two-dimensional diagnostic and visualization tools, a new high-speed stereo vision technique for 3-D measurement is provided based on the stereoscopic methodology in this paper.In this thesis, the studies as follows,A high-speed stereo vision system which consists of a high-speed digital camera and a stereo adapter is demonstrated. Two perspective views of the object are projected onto a single CCD target plane due to the use of the stereo adapter which is attached to the front lens of the camera.Automatic imaging matching technique is adopted to overcome the very challenge problem of stereo object features matching. And the reconstruction model of object feature is built based on stereoscopic methodology.The 3-D geometry of flame surface and the eddies in the flame surface were reconstructed and the 3-D velocity field of the flame surface was described and discussed using the stereo vision system.The 3-D structure and dynamic characters of the two-phase flows were also achieved and discussed based on high-speed stereoscopic imaging at the end of the paper. In summary, a novel technique for 3-D structure reconstruction is provided based on high-speed stereoscopic imaging in this paper. The structure and dynamic characteristics of the flame surface front and the two-phase flows are studied using the technique and error analysis to evaluate the accuracy of the technique is also included in this paper. The results prove that the applied technique is available for study on 3-D reconstruction of the turbulent flows.