Batuhan Aktas

Accurate modelling of carbon dioxide (CO₂) dispersion and infiltration into buildings is essential for assessing the risks associated with accidental releases from carbon capture, utilisation, and storage (CCUS) infrastructure. This study presents an integrated analytical and computational framework for evaluating CO₂ infiltration, incorporating a modified equation of state (EOS) to account for non-ideal gas behaviour. The original infiltration model, based on wind- and buoyancy-driven ventilation, is extended using a virial EOS. Key performance metrics are used to validate the model against experimental data and computational fluid dynamics (CFD) simulations. A comprehensive set of 30 case studies is used to assess model performance across a range of building geometries and environmental conditions. Results show that the modified EOS has minimal impact on far-field predictions, confirming the robustness of the ideal gas assumption under ambient conditions. Importantly, the study finds that CO₂ impurities do not significantly affect far-field dispersion once ambient pressure is reached, though they may influence near-field behaviour at the release point.

This study aims to demonstrate the merits of pressure-relieving holes at the tip region of propellers, which is introduced as “PressurePores^TM” technology as a retrofit on marine propellers to mitigate tip vortex cavitation noise for a quieter propeller. Shipping noise originates from various sources on board a vessel, amongst which the propeller cavitation is considered to dominate the overall radiated noise spectrum above the inception threshold. Thus, by strategically introducing pressure-relieving holes to modify the presence of cavitation, a reduction in the overall cavitation volume can be achieved. This mitigation technique could consequently result in a reduction of the radiated noise levels while maintaining the design efficiency as much as possible or with the least compromise. The strategic implementation of the holes was mainly aimed to reduce the tip vortex cavitation as this is one of the major contributors to the underwater noise emissions of a ship. In this paper, the details and results of a complementary numerical and experimental investigation is presented to further develop this mitigation concept for underwater radiated noise (URN) and to validate its effectiveness at model scale using a research vessel propeller. An overall finding from this study indicated that a significant reduction in cavitation noise could be achieved (up to 17 dB) at design speed with a favourable strategic arrangement of the pressure pores. Such a reduction was particularly evident in the frequency regions of utmost importance for marine fauna while the propeller lost only 2% of its efficiency.

Author(s): Roslynna Roslia, Weichao Shib, Batuhan Aktasb, Rose Normanc, Mehmet AtlarbaUniversiti Teknologi Brunei, Ba

Conducting noise trials with big merchant vessels could constitute serious economic and time losses for the ship operators. This study aims to introduce an experimental acoustic–visual device enabling economical and cost-effective noise trials in full scale. Noise emission and dynamics of propeller cavitation are investigated on a research vessel equipped with a customized submerged device called “Hydropod” that consists of hydrophones and a high definition, wide-angle underwater camera. Previously conducted noise trials following the international standards with an off-board hydrophone array are utilized for the validation of the adopted approach. The comparisons between the Hydropod measurements and conventional noise trial measurement results have shown promising correlations, except for a self-noise hump present in the noise spectra of the Hydropod measurements. Furthermore, by taking advantage of the replacement of the conventional propellers of the catamaran with a set of new profile technology (NPT) propellers, additional trials were conducted using the Hydropod. This enabled interpretation of the relative performance of both sets of propellers in terms of acoustics and cavitation extent. The NPT propellers were superior compared to the conventional propellers over the cavitation extent and resulting acoustic emissions.