bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase-field formulated meshless simulation of Rayleigh-Taylor instability problem
Authors: Rana K B , Mavrič B , Šarler B 
Published: June 2024

Abstract
The interface between two immiscible Newtonian liquids with different densities and the same viscosity, influenced by gravity, is based on the Phase-Field Method (PFM) formulation. The solution of the related governing coupled Navier-Stokes (NS) and Cahn-Hillard (CH) equations is structured by the meshless Diffuse Approximate Method (DAM) and Pressure Implicit with Splitting of Operators (PISO). The variable density is involved in the inertial and buoyancy terms (non-Boussinesq formulation). The related moving boundary problem is handled through single-domain, irregular, fixed node arrangement in two-dimensional Cartesian coordinates. The meshless DAM uses weighted least squares approximation on overlapping subdomains, polynomial shape functions of second-order and Gaussian weights. Implicit time discretisation is performed for the NS and CH equations in the momentum predictor and Phase-Field (PF) variable corrector steps of PISO, while the momentum corrector steps solve the NS equation explicitly. This solution procedure has improved stability compared to Chorin’s pressure-velocity coupling, previously used in meshless solutions of related problems. The Rayleigh-Taylor instability problem simulations are performed for an Atwood number of 0.76. The DAM parameters (shape parameter of the Gaussian weight function and number of nodes in a local subdomain) are the same as in the author’s previous studies on single-phase flows. The simulations did not need any upwinding in the range of the simulations. The results compare well with the mesh-based finite volume method studies performed with the open-source code Gerris.
Joule heating analyses in electrically conductive micro/nano-sized structures
Authors: Sladek J , Sladek V , Repka M 
Published: June 2024

Abstract
Joule heating is occurred in electrically conductive materials. In cracked structures with high concentration of electric current at the crack tip vicinity the Joule heating can be extremely high and even a melting of metal can be observed. It is interesting to investigate thermal stresses caused by this local heating. In micro/nano-sized structures the overheating of structures can be very fast and structure can be damaged. However, in these small structures it is observed the size effect for both heat transport and also for the mechanical balance equation. The thermal transport cannot be described by the classical Fourier’s equation in materials with an internal structure. For mechanical problem due to the size effect the strain gradients have to be considered in the constitutive equations. Then, governing equations for both problems are given by partial differential equations with order of derivatives being higher than in classical case. The collocation mixed FEM is developed here for this multi-physical problem. The present computational method is applied to some crack problem to illustrate compressive stresses at the crack tip vicinity, which are leading to the crack closure.
Fourth-order phase-field simulation of cracks using strong form meshless method
Authors: Ali Izaz , Vuga Gašper , Mavrič Boštjan , Hanoglu Umut , Šarler Božidar 
Published: June 2024

Abstract
The prediction of crack propagation in fracture mechanics is still a fundamental challenge. In recent decades, phase-field formulation emerged as a powerful tool for the simulation of crack evolution, which offers a continuous representation of cracks from intact to broken material. For the first time, the present study combines a fourth-order phase field and a strong-form meshless method to investigate crack propagation in brittle elastic material. The local radial basis function collocation method, structured with the augmented polyharmonic splines, is used to solve the coupled mechanical and phase-field models. Due to the smooth nature of the fourth-order phase-field model, the sharp transition at the crack surface can be avoided. It is found that the presented method successfully predicts the crack propagation for a material subjected to tensile loading. The obtained results agree well with the benchmark case. Further study will include elastoplastic material behaviour and applications to crack formation in different steel processing steps.
Simulation of temperature field in steel billets moving in the reheating furnace by a meshless method
Authors: Liu Q G , Hanoglu U , Šarler B 
Published: June 2024

Abstract
A simulation of a reheating furnace in a steel production line where the steel billets are heated from room temperature up to 1200 °C is carried out. In this work, governing equations are solved in a strong form by the meshless local radial basis function collocation method (LRBFCM) with explicit time-stepping. The solution of the diffusion equation for the temperature is formulated on a two-dimensional central slice of the billet. The temperature field is solved by considering the positions of multiple billets in the furnace and the radiative and convective heat fluxes on the boundaries of the furnace and the billets. Ray tracing procedure, in which the view factors are computed with a Monte-Carlo method, is employed to determine the radiative heat flux. A sensitivity study is performed on the influence of two different stopping times of the billets in the furnace on the temperature evolution.
CFD simulation and geometric optimization of a novel baffle heat sink for power electronics cooling
Authors: T’Jollyn I , Rogiers J , Nonneman J , De Paepe M 
Published: June 2024

Abstract
The electric drivetrain of an electric vehicle typically has two fluid circuits: an oil circuit for lubrication and a water-glycol circuit for cooling. Eliminating the water-glycol circuit can result in a more compact and lighter drivetrain. However, this requires the drivetrain components to be cooled with oil as coolant, which has inferior heat transfer properties compared to water-glycol mixtures. This is particularly challenging for the power modules in the power electronics unit, which exhibit some of the highest heat fluxes in the drivetrain. This study focusses on the design and optimization of a novel type of heat sink for laminar flows with baffles to guide the flow in four different directions. This has two main advantages: the baffles act as fins and increase the heat transfer area and they introduce a swirling motion in the oil thereby disturbing the boundary layers continuously. Computational fluid dynamics simulations using Ansys Fluent are performed to evaluate the thermohydraulic performance of the heat sink. The influence of design parameters such as the height and thickness of both fins and baffles and the baffle spacing in horizontal, upward and downward direction was evaluated by simulations with several combinations of the design space, considering manufacturing constraints. The optimization of the design showed that the fin thickness, horizontal baffle spacing and baffle length should be as small as possible, while there were optimal values for fin height, upward and downward baffle spacing, streamwise baffle spacing and baffle thickness. The simulations show that the thermal resistance of the baffle heat sink can be 19% lower than that of a benchmark pin fin heat sink at equal pumping power.
A novel type of additively manufactured high pressure mini-channel heat exchanger for precooling in hydrogen refueling stations
Authors: Kahlfeld R , Müller F , Müntefering H , Gembarski P , Steinhoff R , Kabelac S 
Published: June 2024

Abstract
During refueling supercritical hydrogen into high pressure storage tanks, the fluid has to be cooled down to temperatures between -33°C and -40°C before entering the vehicle fuel tank. This cooling takes place while the hydrogen is at a pressure of up to 87.5 MPa. The requirements for the heat exchanger performing this task are very high. It has to be pressure resistant, compact enough to fit in the dispenser column and provide a high thermal performance to ensure a fast refueling with high mass flow rates. Only few conventional manufactured heat exchangers are able to fulfil these requirements. With the rise of additive manufacturing technology, especially laser powder bed fusion, new heat exchangers produced without use of conventional joining technologies can be realized. This manuscript presents a new type additively manufactured of mini-channel heat exchanger. It is developed in a joint research project involving the Leibniz University Hanover and an industrial heat exchanger manufacturer. The apparatus has a design pressure of 105 MPa and will be suited to be used in hydrogen refueling stations. The thermal requirements and the design of the apparatus are described. Thermal power and pressure drop for the full-size heat exchanger are calculated via a cell model. Scaled smaller heat exchangers made of 1.4404 stainless steel are additively manufactured via laser powder bed fusion (LPBF). The thermofluiddynamical performance of the scaled apparatus is measured in a testbench to verify the applicability of the used correlations. Deviations in hydraulic diameter and surface roughness are taken into account. Existing correlations are fitted to the new geometry.
Numerical modelling of continuous casting of round billets with turbulence in the melt
Authors: Mramor K , Rek Z , Vertnik R , Šarler B 
Published: June 2024

Abstract
The present work aims to solve the continuous casting benchmark problem in axisymmetry with turbulence in the melt by the meshless method. The physical model of the liquid-solid system that involves mass, momentum and energy conservation is formulated in the mixture continuum approximation. The melt is assumed Newtonian and incompressible. A k-epsilon Reynolds averaged Navier-Stokes turbulence model is implemented with Abe-Kondoh-Nagano closures. The mushy region is modelled as a Darcy porous media with the Kozeny-Carman permeability model. The solution of partial differential equations is implemented locally using collocation with radial basis functions and explicit time-stepping. The velocity pressure coupling is performed using the fractional step method. The validation of the model is assessed by comparing its outcomes with the results of the finite volume method. A sensitivity study of the varying casting speed and temperature on the velocity, temperature, and solid fraction fields is shown.
Nucleation study of xylitol as PCM in two different crystallization systems: a rheometer and a lab-scale prototype
Authors: Navarro M , Lázaro A , Diarce G , Delgado M 
Published: June 2024

Abstract
Sugar alcohols are promising materials for latent heat-based thermal energy systems. Xylitol stands out among them for its high phase change enthalpy and density. However, xylitol, as well as other sugar alcohols, show undercooling and low crystallization rates, which hinder it potential as a phase change material. This work studies the effect of the seeding and shearing technique on crystallization, in addition to the effect of the operation conditions, such as temperature or shear. To do so, two systems are studied: a rheometer and a stirred tank. Induction times are then calculated from temperature and viscosity curves, and a crystallization model is used to study the influence of operating conditions in crystallization.
Experimental and numerical pore-scale characterization of multi-mode heat transfer in porous ceramics exposed to a transverse heat flux
Authors: Briclot A , Lea P , Henry J F , Suter C , Haussener S , Randrianalisoa J 
Published: June 2024

Abstract
We present experimental and computational approaches to characterize the multimode heat transfer in an open-cell Si-SiC foam exposed to a transverse heat flux. The experimental setup consists of a 5×5×10 cm3 parallelepipedal 10ppi foam (83% porosity) placed within a rectangular channel, in which airflow (0-8 g.s−1) was established. The pressure drop across the foam was measured and infrared cameras were used to obtain the temperature of the heater plate and the thermal maps of the foam at the outlet and on the top. The computational approach is a 3D pore scale model of flow and multi-mode heat transfer in the channel subjected to the same conditions. A X-ray tomography technique (50 µm resolution) was used to scan the foam structure and subsequent segmentation and binarization of the data resulted to a digitalized volume of the 1000×1000×2000 voxels and about 101 million cells after meshing. The computations were performed using ANSYS Fluent. Laminar or k-ε turbulence models with enhanced wall treatment were used depending on the airflow rate. Finally, the comparison of the numerical results with experimental data shows that the relative deviation of pressure drop is less than 7.1% and that of outlet foam temperature is less than the experimental uncertainties (5-20%). Using similarity with fins, the effectiveness of foam is evaluated around 2.2.
Contact resistance effects on current path and thermal characteristics of Ag-nanowire network
Authors: Tatsumi K , Sugihara Y , Tamai K , Kuriyama R 
Published: June 2024

Abstract
In this study, we measured the temperature distribution of Joule-heated Ag-NW network using thermoreflectance imaging (TRI). Numerical computation was conducted for the electric current flow and heat transfer of the Ag-NW network. The contact electric resistance was obtained by solving the optimization problem to minimize the difference between the temperature distributions of the measurement and computation. The results showed that the contact electric resistance varies over the Ag-NW network at certain magnitude. This variation significantly affected the temperature distribution by defining the current path and producing a non-uniform current distribution.
Conjugate heat transfer analysis of the transient thermal discharge of a metallic latent heat storage system
Authors: Nees F , Pai Y S 
Published: June 2024

Abstract
Thermal energy storage systems utilizing metallic phase change materials exhibit great potential as a technology for mobile applications, offering high storage densities and high thermal discharge rates. First experimental investigations show the functionality and performance characteristics of this system. For a deeper understanding of the thermal discharge, this paper presents a numerical model and analysis of the transient conjugate heat transfer. For validation of the numerical model, the results of the simulations are compared to the available experimental data. The investigated storage is based on an aluminum silicon alloy and a box-shaped graphite container design. In this system, heat extraction is achieved by forced convection of ambient air. The transient thermal discharge was simulated from 650 °C to 100 °C, and the solidification of the storage material at around 577 °C was simulated using an enthalpy-porosity approach. The discharge time and total heat flow show good agreement with the experimental data, indicating the model’s successful validation. An empirical study was carried out to determine the thermal contact resistance at the interface between the storage material and the graphite container. The present study contributes new physical insights regarding the thermal discharge of a novel metallic latent heat thermal energy storage system.
Exploring the potential and challenges of phase change materials in future heat storage systems via computations and experiments
Authors: Carnie J T , Hardalupas Y , Sergis A 
Published: June 2024

Abstract
The current work describes computational and experimental efforts to enable new heat storage technologies. Approximately 50% of the energy consumed globally is used to generate and manage heat. This is still predominantly acquired from the combustion of fossil fuels, consequently generating just over 40% of the total global CO2 emissions. To achieve a sustainable future, there is a need for sustainable, decarbonised and dependable energy sources. Heat storage is a key technology that could help achieving this goal. Recently published work by the current authors has shown the importance of heat storage in decarbonising heating (and cooling) of buildings using phase change materials (PCMs). The black-box approach followed evaluated the energetic, cost, and environmental impacts of a novel concept PCM storage scheme with microgeneration. The results obtained showed that this system had advantages over current and future competing heating technologies. However, PCM technology remains at low technological readiness levels because of the lack of understanding of the complex heat transfer physics associated with their phase change transition. For example, understanding and characterizing the propagation of the solid-liquid front during charging and discharging in such heat storage modules will be important in predicting and optimising their performance. In the current work, computations have been performed to understand and optimise the effects of container geometry and size on the charging and discharging heat flux profiles of a simple heat storage module. Furthermore, fundamental experiments have also been implemented to identify the complex governing mechanisms of heat transfer and storage in such materials during transient operation.
Numerical investigation of phase change material integration in structured thermocline systems for concentrated solar power
Authors: Sanmartí Oriol , Vera Jordi , Torras Santiago , Pérez-Segarra Carlos D. 
Published: June 2024

Abstract
The integration of encapsulated PCM in a structured thermal energy storage system is studied. The fluid and filler material are discretized using a one-dimensional approach, while the PCM is discretized two-dimensionally. The accumulated energy for the height percentage of PCM and cutoff temperature differences are obtained for three PCMs, NaNO3, KOH and H380, to obtain the best options to enhance the accumulated energy using encapsulated PCM.
Influence of PCMs on thermal performance of wet fire protective clothing
Authors: Malaquias André Fonseca , Campos J B L M 
Published: June 2024

Abstract
The inclusion of phase change materials (PCMs) in firefighting protective clothing (FPC) has been previously shown to be beneficial during the exposure stage, but detrimental in the post-exposure, mainly due to PCM latent heat release towards the skin, after the exposure. It is unclear whether that is also the case for when the FPC is wet. Hence, in this study, a one-dimensional numerical approach is used to study the effect of PCM parameters (PCM mass, melting temperature) and global heat flux, on the thermal performance of a wet fire protective clothing. It is concluded that under wet conditions, the PCM amount, and its phase change temperature have a significant effect on thermal performance, depending on the heat exposure scenario considered. Great benefits are observed in introducing PCMs to prevent water condensation near the skin, but at the cost of greater PCM re-solidification skin damage.
Analyzing the impact of using phase change materials on energy consumption in buildings: A case study
Authors: Hrnčić B. , Vušanović I. 
Published: June 2024

Abstract
The use of phase change material (PCM) in buildings has been shown to be a promising method for reducing energy consumption. This study investigates the effectiveness of using PCM in reducing energy consumption in a typical residential building located in Podgorica, Montenegro, a city with mild winters and hot and dry summers. EnergyPlus software was used to simulate the thermal performance of a building with and without the incorporation of PCM. Building models were created in a way to incorporate PCM in form of a panel, and simulations were done with five different types of PCM, five different thicknesses and three different positions (outside, inside and middle of building envelope). The simulations were performed over a one-year period to account for seasonal variations in temperature and humidity. The simulation results indicate that the use of PCM in buildings design can significantly reduce energy consumption in buildings located in climates similar to Podgorica. This approach can also lead to a reduction in greenhouse gas emissions associated with energy consumption. These findings provide valuable insights for building designers and policymakers looking to reduce energy consumption and improve the sustainability of buildings. In conclusion, the results of this study support the use of PCM in building design as an effective strategy for reducing energy consumption and greenhouse gas emissions in buildings. Further research is needed to investigate the cost-effectiveness of using PCM in buildings design and to explore the potential for their widespread implementation.
What are sustainable plastics? A review of interrelated problems and solutions to help avoid unintended consequences
Authors: Gonella Sara , de Gooyert Vincent 
Published: June 2024

Abstract
Plastics are affordable and versatile, but there is a growing awareness that they are unsustainable in a number of ways, including concerns about climate, health and biodiversity. A number of solutions are being explored that could enable a more sustainable plastics system. So far, most research has focused on isolated technical solutions that address only one specific sustainability challenge posed by plastics, such as end-of-life management or feedstock alternatives to fossil fuels. Some interventions might mitigate one problem but contribute to another at a different stage of the plastics life cycle. This study is based on a literature review and adopts qualitative system dynamics to analyse the unsustainability of plastics with a holistic, integrative approach. The review shows that there is still no agreed definition of sustainable plastics, so the authors propose one based on inputs from the literature. The paper provides an overview of the impacts of potential solutions on the plastics system, highlighting how some interventions could end up having unintended consequences, perhaps even overshadowing the benefits. The results highlight the need for improved communication transparency between plastics stakeholders and a more vertically integrated, harmonised value chain to effectively implement a sustainability transition in the plastics system.
How suitable are current approaches to simulate flood risk under future urbanization trends?
Authors: Zwirglmaier Veronika , Reimuth Andrea , Garschagen Matthias 
Published: June 2024

AbstractFlood risk in urban areas will increase massively under future urbanization and climate change. Urban flood risk models have been increasingly applied to assess impacts of urbanization on flood risk. For this purpose, different methodological approaches have been developed in order to reflect the complexity and dynamics of urban growth. To assess the state-of-the art in the application of flood risk models under urbanization scenarios, we conducted a structured literature review and systematically analyzed 93 publications with 141 case studies. Our review shows that hydrological and hydrodynamic flood models are the most commonly used approaches to simulate flood risk. Future urbanization is mostly considered as urban sprawl through the adjustment of land use maps and roughness parameters. A low number of approaches additionally consider transitions of urban structures and densification processes in their urbanization scenarios. High-resolution physically based flood models have been advanced and are well suited for describing quantifiable processes in data-rich contexts. In regions with limited data, we argue that reducing the level of detail in flood models and increasing the level of detail in urbanization patterns should be considered to improve the quality of flood risk projections under future urbanization. For this purpose, we also call for the development of integrative model structures such as causal network models that have greater explanatory power and enable the processing of qualitative data.