BENCHMARK EXPERIMENT: A COMPARISON OF INTERFEROMETRY, SCHLIEREN AND SHADOWGRAPH

A direct comparison of images of convection seen in interferometry, schlieren and shadowgraph is presented here.  The physical experiment considered is a differentially heated fluid layer enclosed in a rectangular cavity. In the initial discussion, the temperature difference across the cavity is 10 K in the experiments, while the fluid medium in the cavity is air. The corresponding Rayleigh number has been calculated to be The interferograms, schlieren and shadowgraph images are compared on the right column of Figure 5.19. The fringes of an interferogram are lines of constant temperature. With reference to the discussion in Section Data Reduction, temperature here is to be interpreted as an integrated value over the length of the cavity. It should be noted that fringe shapes in a circular geometry are harder to interpret owing to a change in the geometric path length in a direction the path of the light beam.

Figure 5.19:Comparision of data recovered from the three optical techniques (left column). The corresponding experimental images are shown in the right column. . The solid line in the left column is representative of the trend seen at any vertical section of the image.