Three-dimensional measurement of a flow in a rectangular channel using a photoelastic method

The purpose of this study is to measure the shear rate distribution of a flow in a rectangular by using integrated photoelasticity. We measrued a mixed solution of photoelastic material crystals, cellulose nanoctystal (CNC), to elucidate whether there are any phenomena (trends) peculiar to CNC mixed solution that differ from those to the solid case. In addition, we examine the stress-optic for CNC mixed solution using a high-speed polarization camera to measure the retardation and orientation angles of polarized lights. We compare the experimentally measured retardation distribution and the theoretical secondary principal stress difference distribution based on the analytical solution in steady laminar flow. Results show that retardation, which was not caused by stress, appeared in the CNC mixed solution. We compared the secondary principal stress difference distribution with the retardation distribution offsetting the effect of the retardation specific to the CNC mixed solution. The result showed that the spatial intensity distributions of both agreed with a relative error of 3.84%. We conducted additional verification for different flow rates (10, 20 ml/min). As a result the relative errors were 5.67% and 3.24% for flow rates of 10 and 20 ml/min, respectively.