Numerical Simulations of the Hydraulic Performance of a Breakwater-Integrated Overtopping Wave Energy Converter

OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples.

Research on the Microstructure and Microhardness of 9Cr18 Semi-Solid Billet

Formed in the semi-solid state, materials can obtain unconventional microstructures and properties compared with traditional method. In this paper, semi-solid billet of 9Cr18 steel was obtained through a wavelike sloping plate. Microstructure analysis of the semi-solid billet was conducted through scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). X-ray diffraction (XRD) test and microhardness test were also used to analyze the properties. The results showed that the structure of 9Cr18 semi-solid billet contained globular primary austenite and secondary austenite-Cr7C3 eutectic. Globular primary austenite grains were first formed during partial solidification in the sloping plate, and then the rest liquid metal formed secondary austenite and Cr7C3 eutectic structure surrounding the primary grains. Cr atoms had a concentration in the rest liquid side, which along with C atoms contributed to the formation of the Cr7C3 carbide. Hardness in the primary solid grain area and the eutectic area was about 330 HV and 650 HV, respectively. These specific properties were important for subsequent thixoforming of the functional graded materials.

Effects of Inclined Plate Angle and Length on Semi-Solid Microstructure of Martensitic Stainless Steel

An experimental equipment with inclined plate cooling and shearing had been developed to prepare semi-solid 9Cr18 martensitic stainless steel slurry. The effects of inclined plate angel and length on microstructures refinement and spheroidization in semi-solid 9Cr18 alloy was investigated. The results show that when the molten alloy is flowing along the plate surface, the microstructure of the alloy involves from coarse dendrite to fine spherical grains, the sloping plate can provide sufficiently the undercooling for nucleation and lay a foundation for heterogeneous nucleation to form lots of nuclei of crystal internally and on the sloping plate surface, thus causing the melt to nucleate eruptively. Sloping plate angle and sloping plate length can affect the shear strength and shear time of the flow alloy on the sloping plate and thus influence alloy microstructure. Fine spherical grain in the semi-solid 9Cr18 slurry can be obtained at α=45°and L=600mm, the major grain equivalent diameters are less than 55μm and more than 40% of the grain shape factor is in 0.75, exhibiting better grain fine degree and roundness. Using energy dispersive spectrometer (EDS) to investigate the liquid and solid phase in the 9Cr18 semi-solid slurry, iron content is lower and carbon and chromium content is higher in the liquid phase than in the solid phase which makes it possible to prepare the FGM (functional gradient material) with a high wear resistance in the surface and a good strength and toughness in the center.

A Novel Process for Grain Refining and Semisolid Processing

A novel process for grain refining and manufacture of high quality semisolid slurries ofalloys was developed. The process was proven to refine metal grain remarkably, and the grain sizeof pure aluminum can be refined to the first grade of Chinese refining standard of pure aluminumGB/T 7946.4-1999 ref) . P rimary silicon and eutectic silicon in the hypereutectic Al-Si alloy can bealso effectively refined. This process was used to prepare the billets with small spherical grains orequiaxed grains of Al-6Si-2Mg, AZ91, AZ31 and hypereutectic Al-Si alloys successfully. The p ip es ,profi le s and wire s of 6201, AZ31 and AZ61 alloys were produced by continuous rheo-extrusion.The strips of AZ91, AZ31, and Mg-Sn alloys were prepared by rheo-rolling. As an innovativeprocessing technology with low cost and high efficiency, vibrating sloping plate melt treatment hasgood prospective application in many fields such as rheo-casting, rheo-extrusion, rheo-rolling,metal microstructure refinement, etc.