bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and simulation of ingot solidification with the open-source software Code_Saturne
Authors: Demay C , Ferrand M , Belouah S , Robin V 
Published: June 2020

Abstract
In order to address the issue of macro-segregations in large industrial ingots, a solidification model has been recently developed in Code_Saturne, the general purpose open-source Computational Fluid tablDynamics (CFD) software developed and released by EDF R&D. This model is a liquid-solid mixture model inspired from the pioneer work of Bennon and Incropera, including mass, momentum, energy and species conservation equations. In particular, the energy conservation equation is formulated with the temperature variable, the thermosolutal convection is accounted for through the Boussinesq approximation and the interdendritic flow in the mushy zone is governed by the Darcy’s law. Furthermore, a rigid solid phase is assumed and classical microsegregation models are used featuring lever-rule or Gulliver-Scheil assumptions. At the discrete level, a first-order upwind scheme is implemented with a SIMPLEC approach to solve the velocity-pressure coupling. The other couplings involving temperature and concentration fields are efficiently solved performing sub-loops with a PISO-like approach. The overall scheme is mainly implicit with additional treatments to ensure the equilibrium between the hydrostatic pressure gradient and the buoyant forces, and to deal properly with solid zones. The segregation predictions offered by the model are validated against both academic test case and industrial ingot configurations. A convergence study is also led focusing on time step and mesh size sensitivities.
Numerical investigation of an in-situ observed flow regimes during solidification of an NH4Cl – 70 wt%H2O solution
Authors: Wu M , Stefan-Kharicha M , Kharicha A , Ludwig A 
Published: June 2020

Abstract
A volume-average mixed columnar-equiaxed solidification model, where the dendritic morphology of crystals is described with the dendrite envelope, was developed by the current authors. As an evaluation effort, this model is used to simulate a solidification experiment of ammonium chloride water (NH4Cl – 70 wt%H2O) solution. The solution was cooled in a water cooled copper mould (10×8×1 cm3), and the solidification process and the flow dynamics during solidification were in-situ observed/recorded with a Particle Imagine Velocimetry technique. The striking features of solidification in this experiment are that the crystal morphology is dominant in columnar structure, and typical 4 flow regimes in the bulk solution during solidification appear: pure thermal convection (TH), unstable (turbulent) flow caused by double diffusive convection (TU), turbulent-stratified flow (TU-ST), meandering flow (MF). These flow regimes correspond to different cooling/solidification stages, and reflect their interactions with the developing mushy zone. The calculated solidification sequence and the flow dynamics (4 flow regimes) agree with the experimental ones. The experimentally observed phenomena were successfully explained by the simulation.
Influence of crystal fragmentation on the formation of microstructure and macrosegregation during directional solidification under forced convection condition
Authors: Zhang H , Wu M , Zhang Z , Ludwig A , Kharicha A 
Published: June 2020

Abstract
Directional solidification experiment under forced convection condition was conducted. The AlSi7 alloy was solidified in an alumina cylindrical crucible (ø8 mm) in a Bridgeman furnace; and forced convection was induced by applying rotating magnetic field (RMF). The RMF induced flow in the sample during solidification leads to the formation of equiaxed crystals by the mechanism of crystal fragmentation (assumption). The current study is to use a mixed columnar-equiaxed solidification model to simulate this experiment by considering the crystal fragmentation as sole origin of equiaxed crystals. An inward flow (Ekman effect) forms in the front of the (columnar) mushy zone under the RMF. Solute-driven remelting, as enhanced by the interdendritic flow, leads to fragmentation near the columnar tip front. Some fragments are transported by the forced convection to the sample centre and remelted there, while many of them are captured by the columnar structure near the sample centre. The modelling result on the mixed columnar-equiaxed structure agrees with the post-mortem analysis of as-solidified sample. As conclusion following impacts of the crystal fragmentation on solidification are suggested: (1) it widens the central segregation channel and promotes the formation of side-arms; (2) it leads to the formation of relatively high volume fraction of equiaxed crystals near the sample centre.
Comparison of solidification kinetics of compacted and lamellar cast irons
Authors: Lacaze J , de la Torre U , Sertucha J , Regordosa A 
Published: June 2020

Abstract
Thermal analysis is largely used in cast-iron foundry shops as a means to check melt preparation before casting. It has been suggested that the shape of the cooling curves could be related to graphite form, either spheroidal, lamellar or else compacted. The present work is part of a larger study intended to improve melt control for compacted graphite castings by using controlled additions of sulfur and magnesium. Experiments showing lamellar graphite and their counterpart with compacted graphite have been selected for analysis and simulation of the thermal analysis records. Simulation makes use of the fact that compacted graphite differs from lamellar graphite by the limitation of graphite branching in the former. Solidification of both types of irons may thus be simulated using the same basic growth law for irregular eutectics, though changing the parameters describing the branching capability of the faceted graphite phase. The increase of the undercooling of the eutectic plateau during solidification of compacted cast iron when compared to that of lamellar cast iron could be verified and reproduced by simulation. The limitations of the present approach which assumes the temperature in thermal cups is homogeneous at any time are also pointed out.
In situ observation of austenite coarsening induced by massive-like transformation during solidification in Fe–C alloys
Authors: Yasuda H , Suga T , Ichida K , Narumi T , Morishita K 
Published: June 2020

Abstract
A massive-like transformation, in which δ-ferrite massively transforms to γ-austenite in the solid state, was examined by time-resolved X-ray imaging and X-ray diffractometry on a four-dimensional–computed tomography setup. In the unidirectional solidification of a hyperperitectic steel (0.3 mass% C) at 50 μm/s, δ dendrites, fine γ grains that are produced through the massive-like transformation, and coarse γ grains grow together in the steady state. The massive-like transformation occurred commonly in Fe-based alloys with a peritectic reaction in equilibrium. Time-resolved X-ray diffraction measurements for a peritectic steel (0.18 mass% C) showed that the massive-like transformation induced strains in the γ grains. The fine γ grains coarsened and/or vanished and new γ grains formed. The induced strains were released during coarsening. The results obtained by the observations contribute to building of a physical model for γ grain coarsening.
Modelling of intermetallic layers formation during solid-liquid joining of dissimilar metallic materials
Authors: Glück Nardi V , Greß T , Tonn B , Volk W 
Published: June 2020

Abstract
Joining of dissimilar metallic materials gives rise to the production of components with improved properties. At the joint interface, the formation of brittle intermetallic layers might deteriorate the component application. Therefore, its formation and growth must be well understood and carefully controlled. Numerical simulations assist in the determination of processes parameters to obtain the desired bond characteristics. In solid-liquid joining processes, the melt movement plays an important role und must be accounted in the simulations. In this paper, a mathematical model at the continuum scale is used for the description of the interface formation during solid-liquid joining. The description of convection and advection of the molten alloy and the dissolution of the solid substrate are of interest. The substrate dissolution into the melt alters the local composition of the molten alloy, leading to precipitation of intermetallic compounds on the substrate surface during the solidification process. To account for these phenomena, convection heat transfer with phase transformation and diffusion and reaction at the solid-liquid interface are considered in the mathematical model that is based on conservation equations of mass, momentum, energy and species. The different scale problem is solved by applying a dynamic mesh refinement at the interface to accurately solve the intermetallic layer growth. The model was implemented in OpenFoam® and simulation results for the intermetallic layer thickness as a function of solid substrate temperature (Ts) for compound casting between initially liquid Al and a solid Cu substrate are presented. In general, for Ts initial value ranging from 400 to 700 °C while keeping the initial Al melt temperate at 750 °C, the intermetallic layers thickness increases as Ts increases.
Phase field modelling of dendritic solidification by using an adaptive meshless solution procedure
Authors: Dobravec T , Mavrič B , Šarler B 
Published: June 2020

Abstract
A novel numerical procedure is developed for modelling two-dimensional dendritic solidification in dilute binary alloys. The evolution of the phases and the solute concentration is described by the partial differential equations, obtained from the phase field model. The meshless radial basis function-generated finite difference (RBF-FD) method is used for the spatial discretisation of the partial differential equations. The forward Euler scheme is used for the time-stepping. In order to reduce the computational cost, an adaptive procedure is developed, based on the quad-tree strategy, ensuring the highest density of the computational nodes at the solid-liquid interface. In the procedure, the computational domain is divided into overlapping sub-domains which can be dynamically refined or coarsened. The regular or scattered node distribution with constant node density is used for discretisation of each sub-domain. The h-adaptive procedure is ensured by the constant product between the area of a sub-domain and the computational node density. The accuracy and speedup in comparison to the solution on a uniform node distribution are assessed by solving the benchmark problem for dendritic solidification in dilute binary alloys. The main originality of the model represents the first use of RBF-FD method for the spatial discretisation of the PF equations in combination with adaptive solution procedure. The RBF-FD method can be used on unstructured node distributions, which is especially advantageous in the solution of PF model for dendritic growth, since the solution is very sensitive to the regularity of the node distribution. The developed spatial-temporal-adaptive numerical model represents an accurate and computationally efficient tool for the prediction of the dendrite morphology and micro-segregation during the solidification in binary alloys.
Toward the development of a thermal-stress model of an industrial counter pressure casting process
Authors: Wei C , Ou J , Fan P , Mehr F , Maijer D , Cockcroft S , Zhang Y , Chen Z , A L , Zhu Z 
Published: June 2020

Abstract
It is argued that the Counter Pressure Casting (CPC) process is superior over low-pressure die casting (LPDC) in terms of reducing defects and improving cast product performance. To date, there has been relatively little research conducted on the CPC process to provide reliable data to confirm this argument. In this work, a plant trial has been done on an industrial CPC process using a custom-designed ‘H-shaped’ die to acquire an extensive amount of quantitative process data. The data acquired includes temperatures obtained from within the die, the casting, the surrounding environment, and within specific die cooling channels. The data has been processed and analysed to support the development of a comprehensive thermal-stress model of the casting process in order to better understand and quantify the essential macro transport processes. This paper presents a methodology of a coupled thermal-stress model development on the CPC process, and the preliminary results obtained from the models. The results to-date clearly show the need for a fully coupled thermal-stress analysis for the particular casting geometry and process conditions examined. Some of the challenges associated with the current modelling approach are also identified and potential solutions presented.
Application of multi-phase-field lattice Boltzmann method to semi-solid deformation
Authors: Yamanaka N , Sakane S , Takaki T 
Published: June 2020

Abstract
Mechanisms of semi-solid deformation are crucial for reducing solidification defects. In this study, a multi-phase-field lattice Boltzmann (MPF-LB) model, which can simulate growth of multiple dendrites with liquid flow, solid motion and collision, is applied to semi-solid deformation. An elastic contact is introduced to the MPF-LB model to consider collision of two grains. The semi-solid deformation with globular morphology is simulated in the two-dimension by the MPF-LB method. Through the simulations, high potential of the MPF-LB model as the evaluation method of semi-solid deformation is confirmed.
Progress in the development of a contactless ultrasonic processing route for alloy grain refinement
Authors: Pericleous K A , Beckwith C , Bojarevics V , Djambazov G , Dybalska A , Griffiths W D , Tonry C 
Published: June 2020

Abstract
A high frequency tuned electromagnetic (EM) induction coil can be used to induce ultrasonic pressure waves leading to gas cavitation in alloy melts. This is a useful ‘contactless’ approach compared to the usual immersed sonotrode technique. One then expects the same benefits obtained in the traditional ultrasonic treatment (UST) of melts, such as degassing, microstructure refinement and dispersion of particles. However, such an approach avoids melt contamination due to probe erosion prevalent in immersed sonotrodes and it has the potential to be used on higher temperature and reactive alloys. Induction stirring due to the Lorentz force produced by the coil is an added benefit, allowing for the treatment of large melt volumes, a current limitation of UST systems. At ultrasonic frequencies (> 20 kHz), due to the ‘skin effect’ electromagnetic forces vibrate just a thin volume by the surface of the metal facing the induction source. These vibrations are transmitted as acoustic pressure waves into the bulk and to achieve sufficient fluctuation amplitudes for cavitation, acoustic resonance is sought by carefully adjusting the generator frequency. This is akin to the tuning of a musical instrument, where the geometry and sound properties of the metal, crucible and surrounding structure play an important part. In terms of modelling, this is a multi-physics system, since fluid flow with heat transfer and phase change are coupled to electromagnetic and acoustic fields. The various models used and their coupling are explained in this paper, together with the various complications arising by the physics of cavitation. Experimental validation is obtained on a prototype rig featuring a conical induction coil inserted into the melting crucible containing the various alloys being examined. When resonance is reached, measurements demonstrate strong stirring, evidence of cavitation and finally grain refinement.
Study on the effect of ultrasonic wave amplitude on de-emulsification of crude oil to enhance production process
Authors: Lim C H , Sulaiman S A , Japper-Jaafar A , Bhaskoro P T 
Published: June 2020

Abstract
One of the most challenging issue faced by the oil and gas industry is the formation of crude oil emulsion. The emulsion formation will lead to inconsistency in the production performance, which directly affects the economic growth of the industry. Current, conventional de-emulsification methods such as thermal, demulsifiers, and electrical methods are found ineffective in solving crude oil emulsion problem relativity to expected settling time. Therefore, this research aims to propose ultrasonic wave application method for better separation rate to solve crude oil emulsion problem. The effects of ultrasonic waves are investigated by designed experiment under different operating temperature. The optimum operating conditions are investigated and identified through optimization methods in Design Expert Software. The goals of this research are to achieve maximum water and oil separation and minimize the rag layer thickness. Based on the experiments and results, the best operating condition is at operating temperature of 60 °C at 40 μm of ultrasonic frequency of 20 kHz. These parameters were able to provide 73.3% of water separation rate and 20% volume fraction of oil layer after eight hours of bottle test.
Fluidized bed drying of stingless bee pot-pollen: Performance of swirling distributor
Authors: Halim L A , Basrawi M F , Yudin A S M , Faizal S N 
Published: June 2020

Abstract
Pot-pollen is pollen collected by stingless bee, mixed with honey and bee secretion, and then stored in cerumen pots. Raw pot-pollen contains high moisture content which can lead to excessive fermentation and spoilage. Drying of pot-pollen is needed to preserve them. Typically, elevated temperature can increase the drying performance. However as pot-pollen is heat sensitive, heating above 40 °C is not preferable. Hence, the objective of this study is to explore drying performance of fluidized bed dryer with swirling distributor. The experiment was conducted using three different distributors, a perforated distributor, 45° and 67° swirling distributor, at 1.0 m/s and 1.5 m/s superficial air velocities. The weight of pot-pollen used in this experiment is 50 grams. The drying experiment was conducted at ambient conditions, with no heating being applied to the pot-pollen samples. It was found that 67° swirling distributor at 1.5 m/s superficial air velocity has the highest improvement in terms of drying performance, able to reduce the moisture content from 30.5 % to 18 % for 30 minutes drying time. Hence, using swirling distributor is a suitable enhancement to fluidized bed drying especially for heat sensitive food materials.
Gasification of raw and torrefied empty fruit bunch using bubbling fluidized bed
Authors: Abdul Halim N H , Saleh S , Abdul Samad N A F 
Published: June 2020

Abstract
An experimental study of bubbling fluidized bed gasification process using empty fruit bunch (EFB) as a feedstock has been performed in order to study the effect of gasification temperature on gasification performance. Two types of EFB have been used, which are raw EFB and torrefied EFB at 300 °C. The composition of the synthesis gas, gas yield, low heating value (LHV), cold gas efficiency (CGE), and carbon conversion (CC) was determined and analyzed. In terms of synthesis gas, the composition of hydrogen and carbon monoxide gases were increased while methane and carbon monoxide gases were decreased for raw and torrefied EFB when the temperature is increased from 650 to 900 °C. Meanwhile, the synthesis gas yield was significantly enhanced and reached the maximum value of 1.21 and 1.45 MJ/Nm3 for raw and torrefied EFB respectively, which indicates that the torrefaction process improves the synthesis gas yield. Besides, the LHV for the torrefied EFB at highest gasification temperature is 11.08 MJ/Nm3 which is higher than raw EFB (10.81 MJ/Nm3). However, the value of CGE and CC of torrefied EFB are lower than raw EFB with the different about 3% and 5% respectively.
Integrated reservoir study using well-test deconvolution analysis and well-logging data in a gas condensate carbonate reservoir
Authors: Geravand R , Foroozesh J , Nakhaee A , Abbasi M 
Published: June 2020

Abstract
This paper presents an integrated approach to characterize a gas-condensate carbonate reservoir using the combination of well-test deconvolution analysis, and well logging interpretation. Each set of data from the subject well, namely, petrophysical logs, production logs, surface well tests and drill-stem tests was analysed. Well test analyses was implemented using both pressure-derivative and variable-rate deconvolution techniques. An integrated analysis and interpretation of the results from different sources was performed. This approach was especially beneficial in reducing some uncertainties such as the layered nature of the reservoir, the heterogeneous behaviour, and boundary-dominated flow regimes. The application of deconvolved derivative increased the radius of investigation and duration of original constant-rate pressure from 24 hours to 140 hours, enabling us to detect the possible fault effect at late-times. This method was also used for performance evaluation of an acid treatment job in the wellbore. It was found that after acidizing, the total skin factor was severely reduced from 33 to 1.2, indicating a successful performance of the acidizing job.
Investigation of gap losses in a modified compound parabolic concentrating collector with evacuated tube receiver
Authors: Akhter J , Gilani S I , Al-Kayiem H H , Al-Hassan I 
Published: June 2020

Abstract
Compound parabolic concentrating (CPC) collectors paired with evacuated tube receivers have great potential to supply solar thermal energy for numerous applications operating in the medium temperature range. Optical losses resulting from the gap between inner absorber tube and cusp of reflectors badly affect the performance of such collectors. In this paper, a modified design and optical performance of a CPC collector with evacuated tube receiver is presented. Effect of reflectors truncation on the collector’s parameters including aperture width, concentration ratio and energy collection is also evaluated. Ray tracing simulation is performed to assess the instantaneous and daily energy collection. Optical performance of a cusp type CPC is compared with that of a modified CPC with w-shaped cavity at the bottom of reflectors to evaluate gap losses. Optical power density and daily average energy collection by cusp type CPC was 26% higher than CPC with w-shaped cavity due to relatively larger aperture size. CPC with w-shaped cavity was 11% more efficient than CPC with cusp type reflectors.
Investigation of stability, dispersion, and thermal conductivity of functionalized multi-walled carbon nanotube based nanofluid
Authors: Hussein O A , Habib K , Nasif M , Saidur R , Muhsan A S 
Published: June 2020

Abstract
In the attempt of preparing multi-walled carbon nanotube (MWCNTs), covalent functionalisation (CF-MWCNTs) were applied. The stable thermal conductivity was measured as a function of temperature. A number of techniques, such as FTIR, FESEM and UV-vis spectrophotometer were employed to characterise both dispersion stability and morphology of functionalised materials. By using ultrasonic test time, the highest stability of nanofluids was achieved at 60 minutes. As a result, the thermal conductivity displayed by CF-MWCNTs was higher than distilled water. In conclusion, improvement in thermal conductivity and stability displayed by CF-MWCNTs was higher, while the best thermal conductivity improvement was recorded at 31%.