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The thermomechanical phenomena that occur during DC casting of aluminium billets can have a significant impact on the quality of the ingot. Under specific stress conditions hot tearing and cracking of ingot can occur. A large deformation... more
The thermomechanical phenomena that occur during DC casting of aluminium billets can have a significant impact on the quality of the ingot. Under specific stress conditions hot tearing and cracking of ingot can occur. A large deformation of the billet can lead to its instability and to the change in heat transfer efficiency on the boundary, which can lead to unwanted remelting and melt bleed-outs. Modeling of thermomechanical phenomena during this process is not trivial due to involved strong thermomechanic coupling. In addition to elastic deformation the strain field also has contributions from viscoplastic creep, plastic deformation and thermal expansion. All these phenomena occur in nonhomogeneous material with strong temperature dependence of material properties. Many models describing the DC casting process already exist [1] and can provide accurate results. Existing models mainly use the standard finite element method (FEM), which may prove inefficient in some circumstances. T...
The purpose of this work is to determine, based on the computational model, whether a mixture of a binary liquid is capable of producing longer, thinner and faster gas-focused micro-jets, compared to the mono-constituent liquids of its... more
The purpose of this work is to determine, based on the computational model, whether a mixture of a binary liquid is capable of producing longer, thinner and faster gas-focused micro-jets, compared to the mono-constituent liquids of its components. Mixtures of water with two different alcohols, water + ethanol and water + 2-propanol, are considered. The numerical study of pre-mixed liquids is performed in the double flow focusing nozzle geometry used in sample delivery in serial femtosecond crystallography experiments. The study reveals that an optimal mixture for maximizing the jet length exists both in a water + ethanol and in a water + 2-propanol system. Additionally, the use of 2-propanol instead of ethanol results in a 34% jet length increase, while the jet diameters and velocities are similar for both mixtures. Pure ethanol and pure 2-propanol are the optimum liquids to achieve the smallest diameter and the fastest jets. However, the overall aim is to find a mixture with the lo...
The work presents verification of a numerical model for micro-jet focusing, where a coupled liquid and gas flow occurs in a gas dynamic virtual nozzle (GDVN). Nozzlesof this type are usedinserial femtosecond crystallographyexperimentsto... more
The work presents verification of a numerical model for micro-jet focusing, where a coupled liquid and gas flow occurs in a gas dynamic virtual nozzle (GDVN). Nozzlesof this type are usedinserial femtosecond crystallographyexperimentsto deliver samplesintoX-ray beam. Thefollowing performance criteria are desirable: the jet to be longer than 100 μm to avoid nozzle shadowing, the diameter as small as possibleto minimize the background signal,and the jet velocityas high as possible to avoid sample'sdouble X-ray exposure.Previouscomprehensive numerical investigation has been extended to includenumerical analysis of the tip jet velocities. These simulations were then comparedwith the experimental data. The coupled numerical model of a 3D printed GDVN considers a laminar two-phase, Newtonian, compressible flow, which is solved based on the finite volume method discretization and interface tracking with volume of fluid (VOF). The numerical solution is calculated with OpenFOAM based com...
Serial femtosecond crystallography requires reliable and efficient delivery of fresh crystals across the beam of an X-ray free-electron laser over the course of an experiment. We introduce a double-flow focusing nozzle to meet this... more
Serial femtosecond crystallography requires reliable and efficient delivery of fresh crystals across the beam of an X-ray free-electron laser over the course of an experiment. We introduce a double-flow focusing nozzle to meet this challenge, with significantly reduced sample consumption, while improving jet stability over previous generations of nozzles. We demonstrate its use to determine the first room-temperature structure of RNA polymerase II at high resolution, revealing new structural details. Moreover, the double flow-focusing nozzles were successfully tested with three other protein samples and the first room temperature structure of an extradiol ring-cleaving dioxygenase was solved by utilizing the improved operation and characteristics of these devices.
In this paper, a heat transfer problem of continuous casting is solved by two BEM approaches, i.e. front tracking and fixed grid with dual reciprocity. Both techniques are compared and critically evaluated by solving two numerical... more
In this paper, a heat transfer problem of continuous casting is solved by two BEM approaches, i.e. front tracking and fixed grid with dual reciprocity. Both techniques are compared and critically evaluated by solving two numerical examples consisting of determining the temperature field and location of phase change front. Good accuracy has been observed.
Résumé/Abstract A heat transfer problem of continuous casting is solved by two BEM approaches, ie front tracking and fixed grid with dual reciprocity. Both techniques are compared and critically evaluated by solving two numerical examples... more
Résumé/Abstract A heat transfer problem of continuous casting is solved by two BEM approaches, ie front tracking and fixed grid with dual reciprocity. Both techniques are compared and critically evaluated by solving two numerical examples consisting of determining the temperature field and location of phase change front
A numerical model is developed for thesimulationofsolidificationgrain structurefor- mation (equiaxed to columnar and columnar to equiaxed transitions) during the continuous cast- ing process of steel billets. The cellular au- tomata... more
A numerical model is developed for thesimulationofsolidificationgrain structurefor- mation (equiaxed to columnar and columnar to equiaxed transitions) during the continuous cast- ing process of steel billets. The cellular au- tomata microstructure model is combined with the macroscopic heat transfer model. The cellular automata method is based on the Nastac's defini- tion of neighborhood, Gaussian nucleation rule, and KGT growth model. The heat transfer model is solved by themeshless techniqueby using local collocation with radial basis functions. The mi- croscopic model parameters have been adjusted with respect to the experimental data for steel 51CrMoV4. Simulations have been carried out for nominal casting conditions, reduced casting temperature, and reduced casting speed. Proper response of the multiscale model with respect to the observed grain structures has been proved. Keyword: continuous casting of steel, solidifi- cation, multiscale modeling, equiaxed to colum- nar tr...
This paper explores the application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) [1] in solution of coupled heat transfer and fluid flow problems associated with solidification of a binary alloy. The involved... more
This paper explores the application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) [1] in solution of coupled heat transfer and fluid flow problems associated with solidification of a binary alloy. The involved temperature, velocity, species and pressure fields are represented on overlapping sub-domains through collocation by using multiquadrics Radial Basis Functions (RBF). The involved first and second derivatives of the fields are calculated from the respective derivatives of the RBF’s. The energy and momentum equations are solved through explicit time stepping. The pressure-velocity coupling is calculated iteratively, with pressure correction, predicted from the local continuity equation violation [2,3]. The solution procedure is demonstrated in simulation of solidification of 8 wt % Pb-Sn alloy and 5 wt % Sn-Pb alloy in rectangular cavity at conditions, defined in [4]. The numerical examples include studies with different uniform discretization and its...
ABSTRACT This paper explores the application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) in solution of coupled heat transfer and fluid flow problems in Darcy porous media. The involved temperature, velocity... more
ABSTRACT This paper explores the application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) in solution of coupled heat transfer and fluid flow problems in Darcy porous media. The involved temperature, velocity and pressure fields are represented on overlapping sub-domains through collocation by using multiquadrics Radial Basis Functions (RBF). The involved first and second derivatives of the fields are calculated from the respective derivatives of the RBF's. The energy and momentum equations are solved through explicit time stepping. The pressure-velocity coupling is calculated iteratively, with pressure correction, predicted from the local continuity equation violation. This formulation does not require solution of pressure Poisson or pressure correction Poisson equations and thus much simplifies the Kassab and Divo formulation [Divo and Kassab (2007)]. The solution procedure is represented for a steady natural convection problem in a rectangular cavity, filled with Darcy porous media. The numerical examples include studies with different uniform discretization for differentially heated boundaries at filtration Rayleigh numbers Ra F =25, 50, 10 2, 10 3, 10 4, and aspect ratios A = 1/2, 1, 2. The solution is assessed by comparison with reference results of the fine mesh finite volume method (FVM) in terms of mid-plane velocities, mid-plane and insulated surface temperatures, mid-point streamfunction and Nusselt number. The advantages of the method are simplicity, accuracy and straightforward applicability in non-uniform node arrangements.
This paper represents the elements and the use of the simulation system, developed for the Štore-Steel billet caster. The simulation system is used in the context of the state-of-the-art automation and information of the twenty years old... more
This paper represents the elements and the use of the simulation system, developed for the Štore-Steel billet caster. The simulation system is used in the context of the state-of-the-art automation and information of the twenty years old three-strand Concast billet continuous caster for dimensions 140, 180, and 220 [mm] with the capacity of 150.000 [tons/year]. The simulation system is used in the off and in the on-line mode. The off-line mode is used in order to set the proper process parameters and for the redesign of the primary and secondary cooling systems. The numerical solution of the respective models for mass, energy, momentum ans species transfer on the macroscopic and on the microscopic scales are based on the recently developed meshless technology. The options of simulation system, which enable the technologist automatic setup of process parameters, are described. The regulation coefficients were calculated based on this simulation system and installed into the casting m...
Research Interests:
PurposeThe purpose of this paper is to explore the application of the mesh‐free local radial basis function collocation method (RBFCM) in solution of coupled heat transfer and fluid‐flow problems.Design/methodology/approachThe involved... more
PurposeThe purpose of this paper is to explore the application of the mesh‐free local radial basis function collocation method (RBFCM) in solution of coupled heat transfer and fluid‐flow problems.Design/methodology/approachThe involved temperature, velocity and pressure fields are represented on overlapping five nodded sub‐domains through collocation by using multiquadrics radial basis functions (RBF). The involved first and second derivatives of the fields are calculated from the respective derivatives of the RBFs. The energy and momentum equations are solved through explicit time stepping.FindingsThe performance of the method is assessed on the classical two dimensional de Vahl Davis steady natural convection benchmark for Rayleigh numbers from 103 to 108 and Prandtl number 0.71. The results show good agreement with other methods at a given range.Originality/valueThe pressure‐velocity coupling is calculated iteratively, with pressure correction, predicted from the local mass conti...
PurposeThe purpose of this paper is to present the solution of a highly nonlinear fluid dynamics in a low Prandtl number regime, typical for metal‐like materials, as defined in the call for contributions to a numerical benchmark problem... more
PurposeThe purpose of this paper is to present the solution of a highly nonlinear fluid dynamics in a low Prandtl number regime, typical for metal‐like materials, as defined in the call for contributions to a numerical benchmark problem for 2D columnar solidification of binary alloys. The solution of such a numerical situation represents the first step towards understanding the instabilities in a more complex case of macrosegregation.Design/methodology/approachThe involved temperature, velocity and pressure fields are represented through the local approximation functions which are used to evaluate the partial differential operators. The temporal discretization is performed through explicit time stepping.FindingsThe performance of the method is assessed on the natural convection in a closed rectangular cavity filled with a low Prandtl fluid. Two cases are considered, one with steady state and another with oscillatory solution. It is shown that the proposed solution procedure, despite...
ABSTRACT
Over the past thirty years numerical modelling has emerged as an interdisciplinary scientific discipline which has a significant impact in engineering and design. In the field of numerical modelling of transport phenomena in porous media,... more
Over the past thirty years numerical modelling has emerged as an interdisciplinary scientific discipline which has a significant impact in engineering and design. In the field of numerical modelling of transport phenomena in porous media, many commercial codes exist, based on different numerical methods. Some of them are widely used for performance assessment and safety analysis of radioactive waste repositories and groundwater modelling. Although they proved to be an accurate and reliable tool, they have certain limitations and drawbacks. Realistic problems often involve complex geometry which is difficult and time consuming to discretize. In recent years, meshless methods have attracted much attention due to their flexibility in solving engineering and scientific problems. In meshless methods the cumbersome polygonization of calculation domain is not necessary. By this the discretization time is reduced. In addition, the simulation is not as discretization density dependent as in ...
This paper describes the solution of a steady state natural convection problem in porous media by the dual reciprocity boundary element method (DRBEM). The boundary element method (BEM) for the coupled set of mass, momentum, and energy... more
This paper describes the solution of a steady state natural convection problem in porous media by the dual reciprocity boundary element method (DRBEM). The boundary element method (BEM) for the coupled set of mass, momentum, and energy equations in two dimensions ...
Štore Steel Ltd. faces the problem of producing a huge amount (approximately 1400) of different steel compositions in relatively small quantities (approximately 15 tons). This production is performed in batches of predetermined quantities... more
Štore Steel Ltd. faces the problem of producing a huge amount (approximately 1400) of different steel compositions in relatively small quantities (approximately 15 tons). This production is performed in batches of predetermined quantities (50–53 tons). The purpose of this article is to present the methodology for optimizing the production of predetermined steel grades in predetermined quantities before a customer's set deadline in
ABSTRACT
Research Interests:
Research Interests:
This paper represents the elements and the use of the simulation system, developed for the Štore-Steel billet caster. The simulation system is used in the context of the state-of-the-art automation and information of the twenty years old... more
This paper represents the elements and the use of the simulation system, developed for the Štore-Steel billet caster. The simulation system is used in the context of the state-of-the-art automation and information of the twenty years old three-strand Concast billet continuous caster for dimensions 140, 180, and 220 [mm] with the capacity of 150.000 [tons/year]. The simulation system is used in the off and in the on-line mode. The off-line mode is used in order to set the proper process parameters and for the redesign of the primary and secondary cooling systems. The numerical solution of the respective models for mass, energy, momentum ans species transfer on the macroscopic and on the microscopic scales are based on the recently developed meshless technology. The options of simulation system, which enable the technologist automatic setup of process parameters, are described. The regulation coefficients were calculated based on this simulation system and installed into the casting m...

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