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This paper presents an image processing framework for tracking the front of the detonation wave from a sequence of images. The images are captured by high speed camera during a laboratory gas explosion experiment. By tracking the fronts in two or three consecutive frames, it is possible to calculate the thermodynamic properties like velocity and pressure along the entire wave front. Alternatively, these calculations are limited to measurements recorded by sensors at some fixed, locations. An active contour model having Gradient Vector Flow (GVF) as an external force field is used to track the wave front in each image. The structure and the properties of detonations in combustion physics has been the point of interest since early 80's. In the present paper, detonation is studied in the stratified layer of combustible gas above a non-reacting layer of air. The recorded images are digitally processed, and the local velocities are calculated based on the tracked fronts. The calculated velocities are then used to estimate the pressure ahead of the wave front with the help of the normal shock relations. The estimated pressure is compared with the measured values from pressure transducers mounted on the top and bottom of the experiment tube.

The Norwegian petroleum industry has developed a standard for the technical safety of offshore installations (NORSOK S-001, 2008). When dimensioning accidental load with this standard, the deluge or fire water spray may be considered as a risk reducing measure for equipment and pipes, but not for the structural elements or fire partition (NORSOK S-001, 2008). Proper documentation of the suppression effect and reliability has to be provided when water is used as a fire risk reduction measure in risk evaluation. The standard states that the deluge system shall be automatically activated upon confirmed gas detection when used for explosion mitigation.Full-scale fire experiments with fire on offshore platforms are limited by practical and economic considerations. Instead, numerical simulations are used for risk analyses. To get a good representation of the effect of the fire water deluge system, the properties of the water spray need to be known.In the literature, the availability of data on fire water spray is limited. Often the spray is described only by the orifice diameter of the fire water nozzles and spray angle. However, the flow properties of the spray (i.e., size and velocity distribution of the droplets) are known to influence the suppression efficiency. Small droplets will follow the convective forces in the gas flow, evaporate quickly, cool the fire gases and screen for heat radiation. In contrast, large droplets have high momentum and are more likely to reach the source of the fire and to cool objects such as process equipment and pipes.Presently the most used technique for measuring droplet size and velocity in fire water spray is the Phase Doppler Anemometry (PDA). This technique will provide online measurements of both size and velocity at the same time, but the technique has some limitations and practical problems.In this doctoral thesis, a laser-based shadow-imaging technique by a high-speed camera and a laser is used. To analyze the shadow-images, an in-house image-processing tool in Matlab has been developed to find droplet size-and velocity distribution.The results from the experiments in this thesis show the location in the spray to have a large effect on the water flux( 3 ( 2 • ) ⁄ ), i.e. the water flux is not uniform and varies with water supply pressure. The geometry of the nozzle and the frame arms affects the applied water flux extensively at low pressures. This effect is taken into account when the applied water flux is measured. 4The results show the water pressure to have the following effects:  The radial coverage will decrease with increasing water supply pressure  The applied water flux will be less uniform for different azimuthal angles at low water pressures than at high water pressures. The number of large droplets will decrease with increasing pressure  The velocity of the droplets will in general increase with increasing pressure.The research provides unique experimental data of droplet size-and velocity distribution for the fire water nozzle and an image processing ...

This paper presents a framework for processing high-speed videos recorded during gas experiments in a shock tube. The main objective is to study boundary layer interactions of reflected shock waves in an automated way, based on image processing. The shock wave propagation was recorded at a frame rate of 500,000 frames per second with a Kirana high-speed camera. Each high-speed video consists of 180 frames, with image size [$$768 \times 924$$ 768 × 924 ] pixels. An image processing framework was designed to track the wave front in each image and thereby estimate: (a) the shock position; (b) position of triple point; and (c) shock angle. The estimated shock position and shock angle were then used as input for calculating the pressure exerted by the shock. To validate our results, the calculated pressure was compared with recordings from pressure transducers. With the proposed framework, we were able to identify and study shock wave properties that occurred within less than $$300\, \upmu \hbox {sec}$$ 300 μ sec and to track evolveness over a distance of 100 mm. Our findings show that processing of high-speed videos can enrich, and give detailed insight, to the observations in the shock experiments.