On the interaction between oncoming internal waves and a dense gravity current in a two-layer stratification

A series of laboratory experiments was conducted to investigate the dynamics of a dense gravity current flowing down an inclined slope into a two-layer stratification in the presence of oncoming internal interfacial waves. The experiment is set up such that the gravity current propagates towards a wave maker emitting interfacial waves such that the current and waves propagate in opposite directions. The results were compared with the case of gravity current without oncoming waves. The gravity current splits into a portion that inserts itself into the pycnocline as an interflow and another that propagates down the slope as an underflow, with the proportionality depending on the characteristics of the gravity current and the oncoming waves when they are present. The interflow is shown to arise from a combination of detrainment and the preferential insertion of fluid with density greater than the upper layer and less than lower layer along the pycnocline. The mass flux of the interflow is observed to be reduced by the oncoming waves, as waves act to decrease the interflow velocity. The internal waves also increase the path length that the interflow must travel. A combination of reduced velocities and increased path length explains the observed reduction in cumulative flux. The trend of the final cumulative flux is consistent with the mass change observed by comparing density profiles obtained before and after the experiment.

Numerical Simulation of Droplet Impacting and Sliding on Hydrophobic Granular Surfaces

Droplet sliding naturally happens with practical significance in developing artificial self-cleaning surfaces or impermeable barriers. On water-repellent soil surfaces, such processes evolve at very small scales, typically at the particle level. To address this, this paper presents a two-dimensional Lattice Boltzmann (LB) study on the droplet sliding dynamics on a layer of regularly arranged particles with varying size and contact angle (CA) aimed at mimicking conditions comparable to those of real soils. The numerical droplet is initialized above the inclined granular surface with different lifting distances and deposited by gravity. The droplet hits the surface with different impacting velocities and subsequently slides down the slope. Four droplet-sliding behaviors were observed: a droplet sticks to the granular surface, a droplet moves by pinning and depinning of its interface (“stick-slip”), a droplet undergoes periodic elongation and shortening during sliding, and a droplet lifts off the granular surface and may be ruptured. For a droplet that displays the “stick-slip” behavior, the sliding velocity reaches a converged terminal velocity, which increases with a higher CA, a more inclined slope, and a smaller particle size. However, nonunique terminal velocities were identified to be affected by the impacting velocities, but their correlation is not continuous and may not be positive. Finally, we propose to quantify the rotational or translational movement by effective kinematic ratio (EKR), which is defined as the translational kinematic energy divided by the total kinematic energy. The unique relation between the EKR and the terminal velocity is suggested to be one practical indicator to intrinsically characterize the water repellency at the particle level.

Effect of Grain Refiner on Microstructure of Semi-Solid A356 Aluminium Alloy

Grain refining has been studied in the semi-solid-metal (SSM) casting by addition of master alloy Al-5Ti-1B using inclined slope. A356 aluminium alloy was melted at 850 °C and poured at 660 °C on the inclined slope into the steel mould. Grain refiner was added in various percentages of 0.2%, 0.5% and 1.0% in A356 aluminium alloy melt. Microstructure and microhardness were characterized using optical microscope and Vicker’s microhardness tester. The addition of master alloy Al-5Ti-1B not only refined but also increased the globularity of the primary α-Al particles. The higher hardness was achieved with 1% addition of master alloy Al-5Ti-1B.

Making Non-Dendritic Structure via Modified Cooling Slope Technique

The cooling slope technique has been developed in recent years, which controls the nucleation and growth of the primary grains during solidification to achieve fine and non-dendritic microstructures. In this study, A356 Al alloys were processed through a modified cooling slope technique to obtain fine, non-dendritic microstructures, in which the cooling rate of the cast crucible was controlled. Three process parameters, namely pouring temperature, inclined slope angle, and the cooling rate of the cast crucible, were varied during the processing. The cooling slope was water-cooled with a constant water flow rate. The solid fraction and the size distributions of the primary grains along the vertical and horizontal positions of the cast ingots were measured individually. The macro-segregation was examined in terms of the distribution of the solid fraction. The yields of the ingots were calculated for studying the efficiency of the cooling slope technique. The effects of the three process parameters on the microstructures, macro-segregation, and yields were studied by the Taguchi method.

PETROLEUM POTENTIAL OF SOURCE BEDS IN THE CUU LONG BASIN

In the Cuu Long basin, three source beds are identified: lower Miocene, Upper Oligocene, upper Eocene + lower Oligocene. They are separated from each other by sand-clay layers. Only Upper Oligocene and Upper Eocene + Lower Oligocene source beds are two main source beds supplying a great part of organic matter into traps. Petroleum source potential of Upper Oligocene source bed (66.30 billion tons) is greater than Upper Eocene + Lower Oligocene bed (29.88 billion tons). Total amount of hydrocarbon has ability to take part in accumulation process at the petroleumbearing traps from Upper Oligocene and Upper Eocene + Lower Oligocene source beds is over 2.19 billion tons and below 1.16 billion tons respectively. Thus, in whole CuuLong basin, source rocks have capacity to produce 96.18 billion tons of hydrocacbon in which accumulation is 3.35 billion tons making up 3.35% production quantity. Applying Monte - Carlo simulation method, using Crystal Ball software to calculate production potential and total amount of organic matter taking part into migration and accumulation process give rather appropriate result with difference level ≤ 1.25%.. Prospecting levels are in the following order: (i)Central lift zone has the greatest prospects, next is Dong Nai lift zone, graben located in north west inclined slope, south east inclined slope, north east area of Tam Dao lift zone finally. (2)Petroleum does not only accumulate in structural, combination traps but also in non-structural traps.