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To investigate the seismic performance of a wind turbine that is influenced by both the ice load and the seismic load, the research proposes a numerical approach for simulating the seismic behavior of a wind turbine on a monopile foundation. First, the fluid-solid coupled equation for the water-ice-wind turbine is simplified by assigning reasonable boundary conditions and solving the motion equation, and the seismic motion equation of the wind turbine is developed. Then, on this basis, we propose a simplified 3D numerical model that can simulate the interactions among the wind turbine, water and sea ice. By conducting shaking table tests, the results demonstrate that the established numerical model is effective. Finally, we investigate the effect of the boundary range and ice thickness on the seismic performance of a turbine under near-field and far-field seismic actions. Research results illustrate that ice changes the distribution form of the hydrodynamic pressure. Moreover, the thickness of the ice greatly influences the seismic behavior, while the influence of the ice boundary range is only within a certain range. Additionally, the ice load decreases the energy-dissipating capacity of the wind turbine, so the earthquake resilience of the wind turbine is significantly decreased.

A three-dimensional (3D) numerical model was developed to explore the intricate aerodynamic mechanisms associated with aerosol jet printing (AJP). The proposed approach integrates computational fluid dynamics and discrete phase modeling, offering a comprehensive understanding of the deposition mechanisms of the AJP process. Initially, numerical solutions of the governing equations were obtained under the assumptions of compressible and laminar flows, facilitating an analysis of certain key flow variables, in this case, the sheath gas flow rate and carrier gas flow rate across the fluid domain. Subsequently, incorporating a Lagrangian discrete phase model allowed a detailed examination of the droplet behavior after nozzle ejection, considering the influence of the Saffman lift force. Finally, experiments were performed to elucidate the influence of key flow variables on the printed width. Generally, the measured printed line morphology and corresponding line electrical performance exhibited close conformity with the numerical model, demonstrating that the proposed numerical model is important for making well-informed decisions during process optimization.

This paper analyzes the effects of topographic amplification of seismic action in mountain ranges. Theoretically, amplification might be an issue for avalanches, landslides, and rockfall, which seismic events could trigger. The authors conducted a numerical and experimental analysis on a kilometre scale of a Gran Sasso mountain range segment in Italy. A three-dimensional finite element was created using a digital elevation model of the mountain. This model was used to predict the modal parameters of the terrain rockmass, validated against the experimental ones predicted using operational modal analysis, with an improved version of stochastic subspace identification to characterize the mode uncertainties. The modal analysis results were used to calibrate two-dimensional and mono-dimensional equivalent models used for local seismic response analyses. The surface geotechnical model was assumed based on microtremor measurements. The study helps to clarify the true extent of topographic amplification for a case study known in the literature in the context of seismic triggering of avalanches. The results reveal the presence of a combination of macro, meso and microscale amplification effects.

Simulation of the behavior of carbon nanotubes (CNTs) can become a very challenging task considering their complicated shape and large aspect ratio. This study aims to elucidate the role of CNT shape, length, and connectivity during heat transfer in CNT dispersions through a three-dimensional (3D) simulator. Three characteristic shapes for the CNTs are considered, namely, straight, moderately curved, and strongly curved. The results reveal that the commonly used assumption of viewing CNTs as straight cylinders leads to significant overestimation of the overall medium conductivity. The CNT length has an important effect on the nanofluid conductivity for all types of CNT shapes considered here. In addition, use of CNTs with higher conductivity than a certain value appears to have no further beneficial effect, thus relaxing the need for extremely pure or single-wall CNTs. On the contrary, the conductivity remains a strong function of the CNT concentration and may be even increased upon organization of CNTs into loose clusters. The overall approach and concept can be extended to CNT composites in a straightforward manner.

Zengwen Reservoir, the largest water resource in Taiwan, has been seriously impacted by sedimentation, contributed mainly by typhoon floods. Therefore, it is chosen as a case study to investigate the effectiveness of an integrated reservoir management strategy of sediment routing and removal by constructing a dredged guiding channel to route turbidity currents generated during typhoon floods. The strategy is evaluated by simulating flood events of four return periods using a 3D numerical model, the effectiveness of which, with and without the dredged guiding channel, is compared in terms of the venting efficiency of reservoir outlets and the arrival time of turbidity currents. The numerical model is calibrated using the laboratory data and validated using the physical model and field data. The simulated results show a significant increase in the venting efficiency and a decrease in the arrival time of turbidity current for all the flood events in the presence of a dredged guiding channel. In addition, results also aid in predicting trapping efficiency based on the Brune curve trend for different capacity inflow ratios for single flood events. The findings demonstrate the feasibility and effectiveness of the integrated reservoir management strategy in the field before high-intensity flood events.

Using Ground Coupled Heat Pump (GCHP) systems in urban areas can be particularly difficult due to space or legislative constraints, other than excessive costs due to drilling. To overcome these problems, the authors proposed to use Artificial Ground Freezing (AGF) probes, used for tunnel excavation, as Ground Heat Exchangers (GHE). It is a widespread practice to seal the probes in the tunnel after the completion. The conversion of existing AGF probes into GHE for GCHP allows us to avoid additional drilling costs, and other space or legislative constraints associated with the use of GCHP systems in urban areas. Such systems could be developed to use underground urban transportation tunnels for heating and cooling in smart cities. These systems were tested after the construction of two tunnels, as part of the GeoGRID project, in Piazza Municipio, Naples, Italy. The data obtained from the experimental setup have been analysed and used for validation of a finite element model developed by the authors to simulate heat transfer between the probes and the surrounding ground. A simplified pipe flow model was introduced, in combination with a 3D model of the ground, to reduce the complexity and computational effort to solve the discretized equations. The simulation results have been compared with experimental data, showing a good agreement, and observing differences in the range of 2 – 5 %. The model can therefore be used as a predictive tool for the development of this type of innovative heat exchanger.

A three-dimensional numerical model of sand wave dynamics, incorporating the interaction of currents and waves at various angles, has been developed using the Regional Ocean Modeling System (ROMS). This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions. The investigation examines the influence of several key parameters, including the rotation angle of sand waves relative to the main current, tidal current velocity amplitude, residual current, water depth, wave height, wave period, and wave direction, on sand wave evolution. The growth rate and migration rate of sand waves decrease as their rotation angle increases. For rotation angles smaller than 15°, sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%. The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves. As tidal current velocity amplitude and residual current increase, the growth rate initially rises to a maximum before decreasing. The migration rate shows a consistent increase with increasing tidal current amplitude and residual current. Under combined waves and current, both growth and migration rates decrease as water depth increases. With increasing wave height and period, the growth rate and migration rate initially rise to maximum values before declining, while showing a consistent increase with wave height and period. The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents, and reaches its minimum when wave propagation is perpendicular to the currents. This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.

In-pipe water turbines have begun to gain interest for harvesting power on a small scale from pipe networks. However, few studies have addressed the feasibility of installing spherical lift-based helical-bladed turbines in a water supply network. Points such as the pressure drop and generated power remain unexplored. In this study, a three-dimensional numerical model, based on OpenFOAM, is used to investigate the performance of the spherical lift-based helical-bladed in-pipe water turbine. The study aims to evaluate how the geometric properties of this turbine affect its performance in terms of power and efficiency, and the hydraulics of pipe flow in terms of pressure drop. The study considers a turbine of diameter 600 mm, with the following geometric properties: number of helical blades 3, 4 and 5; blade chord length 10%, 15% and 20% of turbine diameter D; blade helicity 0°, 60° and 120°; and pitch angle −6°, −3°, 0° and 3°. These parameters are analyzed at tip speed ratios (TSRs) of 2, 3 and 4. The results show that the five-blade turbine yields a power of 1300 W, while the three-blade turbine yields only 870 W, at an optimum TSR of 3. A change in the chord length of 50% (from 0.10D to 0.15D) increases the turbine power by 88.4% and efficiency by 40% for the same TSR. A further change to 0.20D gives no significant improvement in efficiency or power output. An increase in the helical angle from 0° to 120° results in a 22.8% reduction in turbine power. The turbine achieves the maximum power output of 1350 W at zero pitch angle, with a corresponding efficiency of 27%. The maximum head loss observed is 1.6 m, which represents 2.7% of the total head in the pipe. Solidity has a more pronounced effect on head losses than helicity and pitch angle.

In this study, a three-dimensional numerical model was developed to simulate the complex dynamic phenomenon of railway tracks and to predict the free-field ground vibrations. The dynamic forces of the wheel-rail were expressed as a function of the wavelength and the amplitude of track irregularity, and a user-developed subroutine was also developed to discretize the moving load according to train speed and the length of the traveled element. Then, a 3D finite differences model was validated using in situ measurements. The validated numerical model was extended to study the effect of train speed, rail irregularities, and soil stiffness on vibration levels. The results revealed that faster trains produce larger vibrations that exceed the human threshold even at a distance of 15 m from a railway track of good quality. The poor track generated severe ground vibrations above the human and structural thresholds at significant distances from railway tracks. Moreover, it was found that increasing soil stiffness by ten times leads to a noticeable decrease in the vibration amplitude by about 40%. The developed 3D numerical model provides a valuable tool for preventing the undesired impacts of vibrations on the nearby environment.

Railway lines require a significant amount of natural raw materials. Industrial by-products can be used instead, reducing the costs of natural aggregate exploration. This work analyzes a ballasted track’s short- and long-term performances when replacing conventional sub-ballast aggregate with steel slag. After an extensive laboratory characterization of the steel slag, the material performance was analyzed in a 3D numerical model of a ballasted track when included in a railway track. An empirical model was implemented and calibrated to predict the long-term permanent deformation induced in the track after many train passages. The results are compared with the allowable deformation limits required for conventional high-speed ballasted track railway lines. An additional analysis was conducted to assess the influence of steel slags on the critical speed of conventional railway tracks when used. The results show a residual impact on the critical speed value compared to the conventional sub-ballast made with natural aggregates.