A Quantitative Comparison of Background Oriented and Conventional Schlieren Visualization
Julia A. Dobrosotskaya, Abdulaziz Alrefaie, Bryan Eric Schmidt · AIAA SCITECH 2023 Forum · 2023
View Video Presentation: https://doi.org/10.2514/6.2023-2439.vid We apply background oriented schlieren (BOS) and conventional schlieren techniques to the same two flows--a turbulent heated jet and a laminar thermal plume--with the same field of view and magnification in order to directly qualitatively and quantitatively compare the two methods. While BOS is a simpler system to set up and use, the images reveal two distinct drawbacks. The flow is slightly out of focus by necessity, and so small-scale features are sacrificed. Second, visualization artifacts are present outside of the flow regions in the images. The second half of this paper analyzes these artifacts and we show that they are a direct result of camera sensor noise. Furthermore, the artifacts have a Gaussian distribution with a standard deviation proportional to the standard deviation of the sensor noise itself, which is also Gaussian distributed. Finally, we develop a method to remove the artifacts and show that it is significantly more effective than standard denoising techniques such as total variation regularization.