The Selective Laser Melting (SLM) fabrication process is complex and it is crucial to understand the phenomena that will occur to better control it. In this paper, an FE model on SLM that considers ...powder-to-solid transition together with an effective method to achieve volume shrinkage and material removal has been created. Experiments were conducted to validate the model. A detailed discussion on the progression of the melt pool and the rate of temperature change has been made. Parametric study with the laser power and scan speed as variables has been conducted to identify their relationships with the melt dimensions, melting and evaporation of powder and rates of temperature change.
To intensify the charging rate of thermal storage, new honeycomb configuration has been utilized in this work. The various material were utilized for solid structure namely: Stainless steel (SS); ...Aluminum-6061-T4 (Al-6061) and pure aluminum (Al). The holes were filled with mixture of paraffin (RT82) and Al2O3 nanoparticles. To create various configurations of holes with honeycomb shape, the geometric factor (b2) has three levels and another geometric factor was calculated to reach the equal volume of paraffin in all geometries. Characteristics of NEPCM were measured based on homogeneous model. The two dimensional laminar melting process was simulated based on finite volume approach. The size of mesh and value of time step have been optimized to decrease the computing price and precision of code was tested with matching the data with exist published article. With decrease of b2, the thickness of honeycomb reduces and number of holes increases. When b2 = 1 mm, the required time decreases around 90.87% and 24.28% with changing the material from SS to Al and Al-6061. With utilize of Al, the melting time decreases around 27.96% with reduce of b2. The lowest period is about 6.548 min which belongs to case with pure aluminum and b2 = 1 mm.
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•To improve the charging rate, new honeycomb configuration was applied.•The holes were filled with mixture of paraffin (RT82) and Al2O3 nanoparticles.•The minimum required time is about 6.548 min.•Required time decreases around 90.87% with material alters from SS to Al.
Fog has drawn much attention from scholars and the public; it can reduce visibility to less than 1 km and affect air, sea, and land transportation and economy. In late winter and spring, fog events ...frequently affect intensive human activity in the coastal areas of Eastern China. In this study, numerical simulations from the Weather Research and Forecasting model were combined with observations to investigate the effects of aerosol on the microphysical properties of fog over the Taiwan Strait in April from 2015 to 2017. The mean values of observed liquid water content, number concentration of fog droplets, and mean diameter fog droplets were 0.11 g/m3, 2.2 × 108 #/m3, and 13.9 μm. The observed relationships between fog microphysical properties were close to the simulation results in the urban aerosol experiment, suggesting that the fog events at Kinmen were significantly affected by urban aerosols. The simulation results indicated that the wind blew from the south, and the air temperature was about 1°C higher than the sea surface temperature on foggy days. A stable condition accompanied by a shallow planetary boundary layer was favorable to fog formation. In the urban aerosol experiment, higher number density of aerosols resulted in more but smaller droplets and increased the LWC. An increase in aerosols reflected shortwave radiation, resulting in a colder and wetter atmosphere during fog events in the daytime. This led to a thicker fog layer and an increased number of fog droplets in the urban aerosol experiment. Foggy days and microphysical properties at Kinmen significantly differed between the studied years. As suggested by the correlations between fog-day anomalies and the corresponding Niño 3.4 index and Oceanic Niño Index, this interannual difference might be attributable to the 2015 to 2016 El Niño–Southern Oscillation (ENSO). Further observations are required to ascertain the relationship between fog events, fog microphysics, and ENSO events.
•Aerosol impacts on fog microphysics were explored by simulations and observations.•Warm and humid air mass and stable conditions were favorable to fog formation over the Taiwan Strait.•Higher number density of aerosols resulted in higher Nd, higher LWC, and lower Dd.•Interannual variability of fog days might be attributable to ENSO.
In order to reach Europe׳s 2020 and 2050 targets in terms of greenhouse gas emissions, geothermal resources will have to contribute substantially to meeting carbon-free energy needs. However, public ...opinion may prevent future large-scale application of deep geothermal power plants, because induced seismicity is often perceived as an unsolicited and uncontrollable side effect of geothermal development. In the last decade, significant advances were made in the development of models to forecast induced seismicity, which are either based on catalogues of induced seismicity, on the underlying physical processes, or on a hybrid philosophy. In this paper, we provide a comprehensive overview of the existing approaches applied to geothermal contexts. This overview will outline the advantages and drawbacks of the different approaches, identify the gaps in our understanding, and describe the needs for geothermal observations. Most of the forecasting approaches focus on the stimulation phase of enhanced geothermal systems which are most prone to generate seismic events. Besides the statistical models suited for real-time applications during reservoir stimulation, the physics-based models have the advantage of considering sub-surface characteristics and estimating the impact of fluid circulation on the reservoir. Hence, to mitigate induced seismicity during major hydraulic stimulations, application of hybrid methods in a decision support system seems the best available solution. So far, however, little attention has been paid to geochemical effects on the failure process and to production periods. Quantitative modelling of induced seismicity still is a challenging and complex matter. Appropriate resources remain to be invested for the scientific community to continue its research and development efforts to successfully forecast induced seismicity in geothermal fields. This is a prerequisite for making this renewable energy resource sustainable and accessible worldwide.
Model geometries of random porous materials Buchele, Felix; Blank, Michael; Pöschel, Thorsten ...
International journal of heat and mass transfer,
12/2024, Letnik:
234
Journal Article
Recenzirano
Odprti dostop
We describe a method for modeling the geometry of random porous materials. The approach enables the independent selection of crucial parameters, including porosity, pore size distribution, pore ...shape, and connectivity. Consequently, it can effectively model a wide range of porous systems. Due to the diverse and systematic variation possibilities, the method is suitable for developing and optimizing porous structures. The geometries can be exported as triangular meshes, facilitating their immediate use in numerical simulation and further digital processing. We showcase the method’s capabilities by minimizing the foam structure’s thermal conductivity through geometry optimization.
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•Method for modeling random porous materials’ geometry with flexible parameter control.•Independently select porosity, pore size, shape, and connectivity for diverse modeling.•Versatile, systematic approach for developing and optimizing porous structures.•Export geometries as triangular meshes for simulations and digital processing.•Demonstrated by optimizing foam geometry to minimize thermal conductivity.
•Modeling work of fracture treatment and compositional simulation are introduced and compared.•Measurement of molecular diffusion coefficient in the porous media is reviewed.•Laboratory gas injection ...experiments in shales at the core-scale are detailed.•Pilot tests in the most recent years are summarized.
CO2 injection is a promising method to rejuvenate the shale oil reservoirs after the primary production. In this work, we comprehensively reviewed the CO2 injection enhanced oil recovery (EOR) and carbon storage related literature in shales over the past decade. The aspects reviewed include description of major shale reservoirs producing oil and the necessity to perform EOR, selection of injection scheme, models applied to simulate gas injection, oil recovery mechanisms for different types of gas, molecular diffusion and its laboratory measurement, nanopore effect, adsorption effect on carbon storage and transport, laboratory work of gas injection in shale cores, pilot tests, and economic evaluation. Advanced models in recent years applied to simulate these processes were introduced in details, such as the traditional dual continuum model, the embedded discrete fracture model (EDFM). Heterogeneity effect and upscaling algorithm on the shale oil recovery performance were discussed. Molecular diffusion, as an important flow and oil recovery mechanism, was described regarding its definition, empirical correlation and laboratory measurement with consideration of the porous media effect which is crucial for accurate modeling result. Recovery mechanisms by carbon dioxide, methane and nitrogen were compared at the molecule and pore levels. Pros and cons of different types of gas were evaluated as well. Pore confinement caused by the extremely tiny pores in the organic matter, along with the capillary and adsorption effects were discussed, and approaches to take them into account of the model were addressed. Core-scale gas injection experiments on shales from various institutions were described, and the results were compared. Outcomes of recent pilot tests in the Eagle Ford, and the Bakken formations were summarized, and finally, economic considerations were provided for the feasibility of gas injection in shale oil reservoirs.
This paper summarizes the findings from Phase II of the Offshore Code Comparison, Collaboration, Continued, with Correlation project. The project is run under the International Energy Agency Wind ...Research Task 30, and is focused on validating the tools used for modeling offshore wind systems through the comparison of simulated responses of select system designs to physical test data. Validation activities such as these lead to improvement of offshore wind modeling tools, which will enable the development of more innovative and cost-effective offshore wind designs.
For Phase II of the project, numerical models of the DeepCwind floating semisubmersible wind system were validated using measurement data from a 1/50th-scale validation campaign performed at the Maritime Research Institute Netherlands offshore wave basin. Validation of the models was performed by comparing the calculated ultimate and fatigue loads for eight different wave-only and combined wind/wave test cases against the measured data, after calibration was performed using free-decay, wind-only, and wave-only tests. The results show a decent estimation of both the ultimate and fatigue loads for the simulated results, but with a fairly consistent underestimation in the tower and upwind mooring line loads that can be attributed to an underestimation of wave-excitation forces outside the linear wave-excitation region, and the presence of broadband frequency excitation in the experimental measurements from wind. Participant results showed varied agreement with the experimental measurements based on the modeling approach used. Modeling attributes that enabled better agreement included: the use of a dynamic mooring model; wave stretching, or some other hydrodynamic modeling approach that excites frequencies outside the linear wave region; nonlinear wave kinematics models; and unsteady aerodynamics models. Also, it was observed that a Morison-only hydrodynamic modeling approach could create excessive pitch excitation and resulting tower loads in some frequency bands.
Peer Reviewed
Meltwater from the Greenland Ice Sheet can alter the continental shelf/slope circulation, cross-shelf freshwater fluxes, and limit deep convection in adjacent basins through surface freshening. We ...explore the impacts on the West Greenland Current and Eastern Labrador Sea with different vertical distributions of the meltwater forcing. In this study, we present results from global coupled ocean/sea-ice simulations, forced with atmospheric reanalysis, that are mesoscale eddy-active (~2–3 km horizontal spacing) and eddy-permitting (~6–7 km horizontal spacing) in the study region. We compare the West Greenland Current in mesoscale eddy-active and eddy-permitting without meltwater to highlight the role of small scale features. Here, the mesoscale eddy-active configuration is then used to assess the change in the Eastern Labrador Sea when meltwater is added to the surface or vertically distributed to account for mixing within fjords. In both simulations with meltwater, the West Greenland and West Greenland Coastal Currents are faster than in the simulation with no meltwater; their mean surface speeds are highest in the vertical distribution case. In the latter case, there is enhanced baroclinic conversion at the shelf break compared to the simulation with no meltwater. When meltwater is vertically distributed, there is an increase in baroclinic conversion at the shelf break associated with increased eddy kinetic energy. In addition, in the Eastern Labrador Sea the salinity is lower and the meltwater volume greater when meltwater is vertically distributed. Therefore, the West Greenland Current is sensitive to how meltwater is added to the ocean with implications for the freshening of the Labrador Sea.
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•Compressible wood adsorbent with ecological merits for oil-spill collection.•Photothermal effect induced adsorption of high-viscous crude oil pollutants.•Nature derived structure for ...efficient adsorption and compressible recovery.•Fast photothermal effect as temperature reach up to 88 °C within 100 s under 1 sun.•Potential mechanisms reveal by Computational Fluid Dynamics calculation.
An efficient collection and recovery of high-viscous crude-oil from oil spillage through an environmental-friendly way is extremely important for water remediation. Herein, a new material of thermally-reduced graphene-oxide coating and decoration of hydrophobic-layer over a compressible wood-sponge was proposed as an adsorbent. Owing to the preferable photothermal conversion, an in-situ solar-assisted thermogenesis process could increase the temperature to 88 °C within 100 s under 1 sun illumination and decrease the viscosity of crude-oil for easy adsorption. The fabricated adsorbent exhibited great performances in separation and adsorption (7.28 g/g–0.801 g/cm3) of oil-spill; with fully active-collection of 50 mL crude-oil within 20 min. Numerical modeling was also employed to gain an in-depth understanding of the adsorption and regeneration processes. The temperature gradient and structural dots subjected to compression stress for both photothermal induced adsorption and compressible recovery of crude oil were investigated as the dominant factors. The adsorbent also exhibited satisfactory adsorption and separation capacities for common light oils and heavy oils. Moreover, the adsorbent could be employed for feasible adsorption in semi-open seawater-environment under light, showing potential for practical treatment of offshore oil-spillage. This work designed a potential route to overcome the dilemma of crude-oil adsorption, due to its inherent high-viscosity, through in-situ photothermal thermogenesis using environment-friendly materials derived from natural wood. The knowledge obtained from this work would help in developing novel adsorbents with applied and ecological merits and further understanding of the related mechanisms.
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