CFD-Based Analysis of Wedges Water Entry under Impact Loads

1053-1056The impact on a falling wedge upon water entry is numerically investigated in this paper. After verified by experimental data, the numerical framework is applied for parametric studies on wedges of different drop heights and different deadrise angles to reveal the interaction behaviour between the wedge and water during impact. Pressure distribution on the wedge surface during the water entry shows that the pressure peak moves up along the surface as impact time increases. It is found that the force peak decrease with the increase of drop height and decrease of deadrise angle of the wedge. The peak positions move positively along the timeline as the increase of deadrise angle while the peak force appears just in a small impact time range for a wedge

ON RESISTANCE REDUCTION OF A HULL BY TRIM OPTIMIZATION

The paper aims at conducting trim optimization for a hull to reveal the influence of trim on wave resistance by a potential-based panel method coupled with a response surface method. First, a numerical program for solving the linear free-surface flow problem of a hull moving with a uniform speed in calm water is built by the panel method. The S60 hull model is used to validate the numerical procedure. Next, calculation for hull is performed with two different trims at a wide range of Froude number; resistance test is conducted to validate the numerical method in demonstrating the influence of trim on wave resistance. Finally, a response surface of wave resistance is constructed with respect to variations of trim and Froude number, using the database of wave resistance calculated by the surface method. In this way, a framework is developed to perform trim optimization. The optimum trim point for the present hull shows a significant improvement in both wave resistance and total resistance, compared with that of even keel and the worst trim point. The optimization framework is proved to be effective in energy saving due to resistance reduction

Large datasets of water vapor sorption, mass diffusion immersed in water, hygroscopic expansion and mechanical properties of flax fibre/shape memory epoxy hygromorph composites

This data article presents four experimental sets of results related to flax fibre composites with epoxy shape memory polymer matrix: water vapor absorption, mass diffusion immersed in water, hygroscopic expansion, mechanical properties. The water vapor absorption tests are described in raw data related to four types of laminates with weights measured at different relative humidity (0%, 9%, 33%, 44%,75%, 85% and 100%). The mass diffusion experiments are related to weights of immersed samples over time. The unidirectional composite hygroscopic expansion is also measured along the fibre longitude and transverse directions. The mechanical properties of flax composite at various temperatures (20°C, 40°C, 60°C, 80°C and 100°C) and humidity environments (50% and immersed) are also described. Load-displacement diagrams of the hygromorph composites are converted into stress-strain diagrams via a compliance calibration, from which the tensile moduli are extracted. The data presented in this article can provide a benchmark for the development of new models, or for the determination of other properties via post processing. The detailed interpretation of the data can be found in [1]. The data is available in the Mendeley Data repository at [2]

Anisotropic, Intermediate Coupling Superconductivity in Cu0.03TaS2

The anisotropic superconducting state properties in Cu0.03TaS2 have been investigated by magnetization, magnetoresistance, and specific heat measurements. It clearly shows that Cu0.03TaS2 undergoes a superconducting transition at TC = 4.03 K. The obtained superconducting parameters demonstrate that Cu0.03TaS2 is an anisotropic type-II superconductor. Combining specific heat jump = 1.6(4), gap ratio 2/kBTC = 4.0(9) and the estimated electron-phonon coupling constant ~ 0.68, the superconductivity in Cu0.03TaS2 is explained within the intermediate coupling BCS scenario. First-principles electronic structure calculations suggest that copper intercalation of 2H-TaS2 causes a considerable increase of the Fermi surface volume and the carrier density, which suppresses the CDW fluctuation and favors the raise of TC.Comment: 16pages, 5figure

Design of ship-engine-propeller simultaneous matching and development of a propeller and engine selecting system

A process to design ship-engine-propeller simultaneous matching is proposed in this paper. The design process treats the whole system as an assembly of the ship-propeller subsystem and the engine-propeller subsystem in which relationships between rotational speed of the propeller and advancing speed of the ship are found and expressed as N-V curves. Furthermore, databases of propellers and engines are established and connected to self developed user interface to calculate simultaneous matching conditions in loops and the matching points are collected to form a selection pool where user can conduct selection. An example to select a propeller and an engine for a 25,000t bulk carrier using the developed selecting system is described and the outputs are listed and analyzed. The selected pair of the propeller and the engine is efficient and comprehensive compared with other instances in the databases

Trim Optimization of Ship by a Potential-Based Panel Method

A surface panel method for a boundary-value problem with the free surface is proposed to predict ship wave resistance under different trim conditions based on a so-called double-model solution. The free surface boundary condition is linearized with respect to the oncoming flow and computed by a four-point finite difference scheme. Sample computation for Wigley hull is carried out to demonstrate the effectiveness and the robustness of the method. A hull model is taken into account at two different displacements with respect to trim conditions of lower wave resistance. It is demonstrated by calculation and experiment that the wave resistance under the trim conditions provided by the proposed method is lower than that under the initial conditions

An experimental study on binderless briquetting of Chinese lignite: effects of briquetting conditions

Technology development of lignite upgrading involving drying and binderless briquetting is important to the efficient utilization of lignite resources. In this study, the effects of briquetting conditions, i.e., briquetting pressure, temperature, coal properties and pretreatment, on the compressive strength of briquettes were systemically investigated using a lab-scale briquetting testing rig. The experimental results indicated that the compressive strength of briquettes increased with increasing the compression pressure. An optimum strength was obtained at the briquetting temperature of 150 °C. There also existed an optimum moisture content of 14–16% at which the highest compressive briquette strength was achieved. The increase in the amount of –125 μm size fraction in the feed sample increased the briquette strength. FTIR analysis showed that the oxygen-containing functional groups have a significant influence on the compressive briquette strength due to the ability of forming more hydrogen bonds

Study on the Single Toxicity of Five Azole Fungicides for Green Algae

Azole fungicides are widely used to control diseases and insect pests of vegetables, fruits and flowers because of their good antibacterial effect and regulating plant growth. However, their extensive use inevitably enters the water environment with rainfall and surface runoff, which leads to potential harm to aquatic organisms. At present, the research on the biological toxicity of azole fungicides mainly focuses on single azole compounds, such as Paclobutrazol, hexaconazole, propiconazole and Difenoconazole. However, the systematic study on the toxic effects of multi-component mixtures of azole fungicides is still very lacking, and it is unable to accurately assess the ecological risk. Therefore, in this paper, five common azole fungicides (imidazole, tebuconazole, triadimefon, tricyclazole and hymexazol) in the environment were taken as target pollutants. Scenedesmus obliquus was used as the toxicity indicator. The mixture system was designed by the equal effect concentration ratio method and linear average ray method. Study the 96h toxicity and interaction of Scenedesmus obliquus under combined stress of azole fungicides. The main research results are as follows:The 96 h toxicity test of five typical azole fungicides to Scenedesmus obliquus was determined by microplate toxicity analysis method. Fitting with Weibull function and taking EC50 as the criterion,the results show that the single toxicity order of the five tested fungicides was:tebuconazole > Triadimefon > oxacillin > Tricyclazole > imidazole

CFD-Based Analysis of Wedges Water Entry under Impact Loads

The impact on a falling wedge upon water entry is numerically investigated in this paper. After verified by experimental data, the numerical framework is applied for parametric studies on wedges of different drop heights and different deadrise angles to reveal the interaction behaviour between the wedge and water during impact. Pressure distribution on the wedge surface during the water entry shows that the pressure peak moves up along the surface as impact time increases. It is found that the force peak decrease with the increase of drop height and decrease of deadrise angle of the wedge. The peak positions move positively along the timeline as the increase of deadrise angle while the peak force appears just in a small impact time range for a wedge