A comprehensive numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles. A paraffin-based nanofluid containing various volume fractions of Cu was applied. The governing equations were solved on a non-uniform mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid-liquid interface. The effects of nanoparticle dispersion in a pure fluid and of some significant parameters, namely nanoparticle volume fraction, cavity size and hot wall temperature, on the fluid flow, heat transfer features and melting time were studied. The results are presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux. The suspended nanoparticles caused an increase in thermal conductivity of nano-enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. In addition, the nanofluid heat transfer rate increased and the melting time decreased as the volume fraction of nanoparticles increased. The higher temperature difference between the melting temperature and the hot wall temperature expedited the melting process of NEPCM.

The principle of virtual displacements (PVDs) extended to elasto-thermo-electric problems includes virtual internal elastic, thermal and electric works. The governing equations have displacement vector, temperature and electric potential as primary variables of the problem, and the elasto-thermal, elasto-electric and pure elastic problems are obtained as particular cases by deleting the appropriate contributions in the general elasto-thermo-electric variational statement. The most sensitive issue is given by thermal coupling because the thermo-elastic and thermo-electric effects change depending on the type of load and analysis considered (mechanical load, temperature or electric potential imposed and free vibration analysis). This feature means that the form of the virtual internal thermal work in such variational statements changes depending on the analysis performed and the load applied. Results about multilayered plates and shells suggest the appropriate extension of the variational statement for each analysis, and they give an exhaustive explanation for several forms of the PVD proposed.

For the designing of cutting-dies is a complex and experience-based process, it is poorly supported by conventional 3D CAD software. Thus, the majority of design activities, including the (re)modeling of those cutting die-components that are directly responsible for performing shaping operations on a sheet-metal stamping part, traditionally still need to be carried-out repetitively, separately, and manually by the designer. To eliminate some of these drawbacks and upgrade the capabilities of conventional 3D CAD software, this paper proposes a new methodology for the development of a parametric system capable of automatically performing a (re)modeling process of compound washer dies’ cutting-components. The presented methodology integrates CATIA V5 built-in modules, including Part Design, Assembly Design and Knowledge Advisor, publication mechanism, and compound cutting die-design knowledge. The system developed by this methodology represents an ‘intelligent’ assembly template composed of two modules GAJA1 and GAJA2, respectively. GAJA1 is responsible for the direct input of the die-design problem regarding the shape, dimensions and material of the stamping part, its extraction in the form of geometric features, and the transferring of relevant design parameters and features to the module GAJA2. GAJA2 interprets the current values for the input parameters and automatically performs the modeling process of cutting die-components, using die-design knowledge and the company’s internal design and manufacturing standards. Experimental results show that this system significantly shortens the modeling-time for cutting the die-components, improves the modeling-quality, and enables the training of inexperienced designers.

A novel sound quality simulation approach was proposed to optimize the acoustic performance of a four-cylinder diesel engine. Finite element analysis, single-input and multiple-output technology, flexible multi-body dynamics, and boundary element codes were used to acquire the hexahedron-element model, experimental modal frequencies, vibration velocities, and structurally radiated noise of the block, respectively. The simulated modal frequencies and vibration velocities agreed well with the experimental data, which validated the finite-element block. The acoustic response showed that considerable acoustic power levels existed in 1500–1900 Hz and 2300–2800 Hz as the main frequency ranges to optimize the block acoustics. Then, the optimal block is determined in accordance with the novel approach, which reduces the overall value, high-frequency amplitudes, and peak values of acoustic power; thus, the loudness, sharpness, and roughness decline to make the sound quieter, lower-pitched, and smoother, respectively. Finally, the optimal block was cast and bench-tested. The results reveal that the sound quality of the optimal-block engine is substantially improved as numerically expected, which verifies the effectiveness of the research approach.

The impacts of rainfall direction on the degree of hydrological response to rainfall properties were investigated using comparative rainfall-runoff experiments on a small-scale slope (4 m×1 m), as well as canonical correlation analysis (CCA). The results of the CCA, based on the observed data showed that, under conditions of both upstream and downstream rainfall movements, the hydrological process can be divided into instantaneous and cumulative responses, for which the driving forces are rainfall intensity and total rainfall, and coupling with splash erosion and wash erosion, respectively. The response of peak runoff (P_r) to intensity-dominated rainfall action appeared to be the most significant, and also runoff (R) to rainfall-dominated action, both for upstream- and downstream-moving conditions. Furthermore, the responses of sediment erosion in downstream-moving condition were more significant than those in upstream-moving condition. This study indicated that a CCA between rainfall and hydrological characteristics is effective for further exploring the rainfall-runoff-erosion mechanism under conditions of moving rainfall, especially for the downstream movement condition.

With the development of ski-jump energy dissipation for high and large discharge among the hydraulic projects, the effects of characteristics of water flow on energy dissipation are increasingly important. In the present study, the effects of aeration and the initial water thickness on axial velocity attenuation of jet flow were analyzed, using variance analysis and numerical calculated methods. From the analysis of test data, both of the air concentration and initial water thickness are sensitive factors for the axial velocity attenuation of jet flow along the axial way, and there is no significant interaction effect between the aeration and initial water thickness. Aeration has a more significant effect on the axial velocity attenuation of jet flow. Decreasing the initial water thickness of jet flow can reduce the length of jet core, and make the initial position of axial velocity attenuation closer to the nozzle exit. The numerical calculation results show that aeration can contribute to the enhancement of entrainment ability of jet flow, which may improve the interaction between jet flow and surroundings. For ski-jump energy dissipation among the hydraulic projects, combining aeration with decreasing initial water thickness of jet flow is an effective way to enhance the rate of axial velocity attenuation.

In water distribution systems, water leakage from cracked water pipes is a major concern for water providers. Generally, the relationship between the leakage rate and the water pressure can be modeled by a power function developed from the orifice equation. This paper presents an approximate solution for the computation of the steady-state leakage rate through a longitudinal line crack of a water distribution pipe considering the surrounding soil properties. The derived solution agrees well with results of numerical simulations. Compared with the traditional models, the new solution allows assessment of all the parameters that related with leakage including the pressure head inside the pipe, hydraulic conductivity, crack size and its position, and pipe size and its depth.

A trajectory imaging based method for measuring the velocity and diameter of coal particles was presented. By using an industrial charge-coupled device (CCD) camera and a low power semiconductor laser, the images of coal particles under relatively long exposure time were recorded and then processed to yield both the velocities and sizes. Fundamental research on this method with special attention to recording parameters, e.g., magnification factor and exposure time, was carried out. For most of the test cases, the results agree with those obtained by particle image velocimetry (PIV) and shadow imaging method. Measurements with good accuracy can be obtained when the imaging magnification factor and exposure time are set appropriately, making N be larger than 3.5, and R between 5–7, where N and R are the number of pixels occupied by the average width and the ratio of length to width of particle trajectory on the image, respectively. The work indicates the feasibility and potential application of the present measurement method for online measurement of coal powder in pipes in industrial power plants.