Modeling of nonstationary gas outflow at breaks of subsea gas pipelines

Numerical modeling of the outflow of an air jet into water with a guillotine rupture of a pipeline by the VOF method using k-ε and k-ω SST turbulence models was carried out. The calculations were carried out in the axisymmetric approximation. The following phases of the outflow process were calculated: the formation of a large gas bubble at the place of the rupture, its growth, the separation of the bubble from the place of rupture, and the formation of a gas jet behind the bubble. It is shown that the rate of bubble detachment in the calculations by the k-ω SST model is higher than that in the calculation by the k-ε model.

Dynamics of bubble growth under a heated substrate

This paper investigates the growth dynamics of a vapor-gas bubble pressed against a heating plate by the buoyancy force. The shadow method was used to capture images, which were then automatically processed to calculate the size of the bubble. As expected, the bubble dynamics significantly depends on the heating power. It was found that the ratio of bubble diameter to bubble height increases as it grows.

Numerical simulation of the surfactants effect on the Taylor bubble in the PHP

Numerical simulation of the motion of a Taylor gas bubble in a heated small-diameter tube is carried out. Two models are used to describe the dependence of surface tension on temperature. In the first model, the surface tension decreases with temperature, and in the second, it increases, which corresponds to pure water and an aqueous surfactant solution. It is shown that the derivative sign affects the thickness of the liquid film around the bubble.

Efficient Detection of Underwater Natural Gas Pipeline Leak Based on Synthetic Aperture Sonar (SAS) Systems

Natural gas is an important source of energy. Underwater gas pipeline leaks, on the other hand, have a serious impact on the marine environment; hence, the need for a reliable and preferably automated inspection method is essential. Due to the high impedance difference and strong scattering properties of gas bubbles in the marine environment, sonar systems are recognized as excellent tools for leak detection. In this paper, a new method for gas leak detection is proposed based on gas bubble acoustic scattering modeling using Synthetic Aperture Sonar (SAS) technology, in which a coherent combination of gas bubble and pipeline scattering fields at different angles along synthetic apertures is used for leak detection. The proposed method can distinguish leak signals from the background noise using coherent processing in SAS range migration. SAS as an active sonar can collect accurate information at wide area coverage rate, independent of operating range and frequency, which can potentially reduce the time and cost of pipeline inspection. The simulation and comparison results of the proposed method based on coherent processing of synthetic aperture technology and the real aperture system show that the proposed method can effectively distinguish gas bubble signals at different ranges even in a single pass and improves pipeline leak detection operations.