An image processing framework for automatic tracking of wave fronts and estimation of wave front velocity for a gas experiment

Abstract

This work presents an image processing framework designed to automatically track the wave front in a sequence of images from a high speed film. A watershed algorithm is used for segmentation and contouring, while an active contour model is used for controlling the flexibility and the rigidity of the contour. The velocity of the wave front is calculated by estimating the displacement of the front in two frames, divided by the time difference between the frames. The calculated velocity is compared with the sensor measurements. Further, the calculated velocities can be used to estimate thermodynamic properties like the Mach number, the pressure and the temperature across the wave. With the purposed framework, these properties can be estimated along the entire wave front. Otherwise, these thermodynamic properties are limited to either theoretical values or to sparse measurements from sensors. The experiment is done by using a shock tube and the film is captured by a high speed camera using the shadowgraph system.