Notes on Numerical Fluid Mechanics and Multidisciplinary Design

Co-authored bookchapter

This chapter introduces techniques for the capture and efficient display
of dynamic three-dimensional non-stationary gas flows. We describe a flexible
Schlieren-tomographic system consisting of multiple consumer camcorders. A special
choice of background pattern for Background Oriented Schlieren (BOS) imaging
provides for flexibility in the experimental setup. Optical flow techniques are
used to measure image space deflections due to heated air flows from arbitrary camera
positions. A specially tailored sparse-view algebraic reconstruction algorithm is
employed to tomographically recover a refractive index gradient field. After robust
integration of these gradient fields, time-varying, fully three-dimensional refractive
index fields are obtained. These can be rendered efficiently using a ray-casting
style algorithm that is suitable for graphics hardware acceleration. Additional optical
properties can be rendered within the same computational framework.