Quantitative reconstruction of 3D flow density fields by a direct computerized tomography method of BOS

Background oriented schlieren(BOS) technology is an efficient measurement method for quantitative diagnostics of fluid field in recent decades, and it has a broad application prospect in flow field measurement. It not only has high spatial and temporal resolution, as well as can be employed for quantitative measurement of the density gradient distributions of convection fields. In this paper, a new method for reconstructing density distributions is proposed. Initially, we obtained the point displacement image according to the basic principle of BOS. Secondly we used the local basis function method to discretize the volume to obtain the coefficient matrix. We had to choose an appropriate finite support basis function to ensure the coefficient matrix was sparse. Finally we obtained the density field by using algebraic iteration method and other methods. Numerical simulation experiments are presented to verify our method. The experimental results of refractive index and density field distribution of flow field are obtained after the simulation experiment, which indicates that the method of CTBOS technology can obtain the quantitative refractive index and density distribution of flow field, while in the real condition, there is great application value.