Shack-Hartmann wavefront sensor for tomographic reconstruction of aerodynamic flow density measurements

This work examines the feasibility of and requirements for using a Shack-Hartmann wavefront sensor based system for the tomographic reconstruction of fluid density in an aerodynamic flow measurement. The sampling and noise requirements are examined at each stage of the measurement process including the Shack-Hartmann sensor, phase reconstruction, and tomographic reconstruction. Based on this analysis, the key design relationships for the Shack-Hartmann sensor are developed. A two-dimensional Shack-Hartmann sensor was designed and built using a commercial of-the-shelf lens array and an 8-bit CCD camera. The characterization and calibration test results are presented. The system capabilities are demonstrated by taking a single projection measurement of a free air jet and a simulated tomographic reconstruction is performed by assuming axial symmetry. The results indicate that the Shack-Hartmann sensor is a viable tool for this type of measurement and that it may be especially well suited to the transonic and subsonic measurement regime.