Visualization is a powerful tool in the investigation of complex physical phenomena, due to the fact that the human visual perception system is well adapted to process complex visual information and extract visual information from images. Frequently, a graphical presentation of data is easier to understand and analyze than the corresponding sequences of numerical data, especially for data sets describing spatial structures of time varying phenomena. Visualized temperature, velocity and flow fields enable a better insight into the process under consideration and they can serve as complement in addition to the quantitative data. Visualization images are obtained using various experimental techniques, they can also be generated from data originating either from point measurements or from numerical simulation. On the other hand, quantitative data can be extracted from images obtained using different experimental visualization techniques. The different imaging techniques have experienced a dramatic development in the past decade, especially due to the rapid development of computer technology which enables fast manipulation of large quantities of data, the solution of complex mathematical models, and it is also a fundament for the implementation of digital image processing techniques in combination with the recording of images with modem video equipment.