Laser absorption tomography based on unstructured meshing

Abstract

Laser absorption tomography (LAT) is an imaging technique used to monitor gas flow and combustion processes. The measurement plane is typically discretized using square pixels in which the flow field is assumed to be uniform. This approach can introduce large discretization errors compared to a finite element mesh with linear interpolation, especially when the domain has an irregular and nonrectangular boundary. In this work, we assess the influence of triangular mesh and quadrilateral mesh schemes on reconstruction accuracy. Our theoretical analysis and numerical studies demonstrate that linear interpolation yields superior performance compared to the conventional uniform-pixel method, and the error can be reduced from 0.250 to 0.097 and 0.160 to 0.105 for triangular and quadrilateral meshes, respectively. Non-body-fitted mesh can increase error by 70% ~ 99%. The experiment also proves the superiority of body-fitted meshes with linear interpolation. Moreover, triangular mesh exhibits better noise immunity than quadrilateral mesh. The reconstruction quality appears to be insensitive to the mesh quality for the quadrilateral mesh.