Material and debris transport patterns in Moreton Bay, Australia: The influence of Lagrangian coherent structures.

Coastal tidal estuaries are vital to the exchange of energy and material between inland waters and the open ocean. Debris originating from the land and ocean enter this environment and are transported by currents (river outflow and tide), wind, waves and density gradients. Understanding and predicting the source and fate of such debris has considerable environmental, economic and visual importance. We show that this issue can be addressed using the Lagrangian coherent structures (LCS) technique which is highly robust to hydrodynamic model uncertainties. Here we present a comprehensive study showing the utility of this approach to describe the fate of floating material in a coastal tidal embayment. An example is given from Moreton Bay, a semi-enclosed subtropical embayment with high morphologic, ecological and economic significance to Southeast Queensland, Australia. Transport barriers visualised by the LCS create pathways and barriers for material transport in the embayment. It was found that the wind field modified both the rate attraction and location of the transport barriers. One of the key outcomes is the demonstration of the significant role of islands in partitioning the transport of material and mixing within the embayment. The distribution of the debris sources along the shoreline are explained by the relative location of the LCS to the shoreline. Therefore, extraction of LCS can help to predict sources and fate of anthropogenic marine debris and thus, serve as a useful way for effective management of vulnerable regions and marine protected areas.

Transport and fate of inhaled particles after deposition onto the airway surface liquid: A 3D numerical study.

In this paper, a numerical investigation is carried out to provide insights into the fate of inhaled aerosols after their deposition on the lung lining fluid in both healthy and diseased states. Pulmonary drug delivery is a well-known non-invasive route of administration compared to intravenous delivery. Aerosol particles are formulated and used as drug carriers, which are then sent to the airways using aerosol drug delivery devices. This approach is useful for site-specific treatment of lung diseases, treatment of central nervous system (CNS) disorders and a variety of other diseases. Bioavailability of the inhaled therapeutic particles after landing on the airway lining fluid can be significantly altered by the lung muco-ciliary clearance, a process through which hairlike structures known as cilia beat in a harmonised manner and induce the mucus in the proximal direction, leading to an effective clearance of the foreign inhaled particles entrapped by this sticky layer from the airways. Here, we set up a 3D computational model of ciliary arrays interacting with periciliary liquid film (i.e. confined between the epithelium and mucus layer) and a detailed analysis is conducted to better understand the fate of drug nanoparticles that are able to penetrate the mucus. Consistent with clinical findings, we find that the actions of cilia result in a low rate of drug retention and absorption by the pulmonary tissues in healthy lungs. However, under conditions associated with abnormal ciliary beats, the retention time of particles is notably increased at the site of release. Nonetheless, the results associated with some of the ciliary impairments reveal that deposition of drug aerosols on the ciliated cells may still be a significant challenge. These findings have potentially important implications on the modification of therapeutic drug particles to achieve a higher absorption rate.

Effect of cold start on engine performance and emissions from diesel engines using IMO-Compliant distillate fuels.

Emissions from ships at berth are small compared to the total ship emissions; however, they are one of the main contributors to pollutants in the air of densely-populated areas, consequently heavily affecting public health. This is due to auxiliary marine engines being used to generate electric power and steam for heating and providing services. The present study has been conducted on an engine representative of a marine auxiliary, which was a heavy duty, six-cylinder, turbocharged and after-cooled engine with a high pressure common rail injection system. Engine performance and emission characterisations during cold start are the focus of this paper, since cold start is significantly influential. Three tested fuels were used, including the reference diesel and two IMO (International Maritime Organization) compliant spiked fuels. The research engine was operated at a constant speed and 25% load condition after 12 h cooled soak. Results show that during cold start, significant heat generated from combustion is used to heat the engine block, coolant and lubricant. During the first minute, compared to the second minute, emissions of particle number (PN), carbon monoxide (CO), particulate matter (PM), and nitrogen oxides (NOx) were approximately 10, 4, 2 and 1.5 times higher, respectively. The engine control unit (ECU) plays a vital role in reducing engine emissions by changing the engine injection strategy based on the engine coolant temperature. IMO-compliant fuels, which were higher viscosity fuels associated with high sulphur content, resulted in an engine emission increase during cold start. It should be taken into account that auxiliary marine diesel engines, working at partial load conditions during cold start, contribute considerably to emissions in coastal areas. It demonstrates a need to implement practical measures, such as engine pre-heating, to obtain both environmental and public health advantages in coastal areas.

Effect of sulphur and vanadium spiked fuels on particle characteristics and engine performance of auxiliary diesel engines.

Particle emission characteristics and engine performance were investigated from an auxiliary, heavy duty, six-cylinder, turbocharged and after-cooled diesel engine with a common rail injection system using spiked fuels with different combinations of sulphur (S) and vanadium (V) spiking. The effect of fuel S content on both particle number (PN) and mass (PM) was clearly observed in this study. Higher PN and PM were observed for fuels with higher S contents at all engine load conditions. This study also found a correlation between fuel S content and nucleation mode particle number concentration which have more harmful impact on human health than larger particles. The highest PN and PM were observed at partial load conditions. In addition, S in fuel resulted in higher viscosity of spiked fuels, which led to lower engine blow-by. Fuel V content was observed in this study, evidencing that it had no clear effect on engine performance and emissions. Increased engine load also resulted in higher engine blow-by. The lower peak of in-cylinder pressure observed at both pre-mixed and diffusion combustion phases with the spiked fuels may be associated with the lower energy content in the fuel blends compared to diesel fuel.