Selective laser melting process is a powder bed fusion additive manufacturing process that finds ... more Selective laser melting process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the end product. This paper investigates the effect of PSD on deformation for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder distribution based on the different particle size distribution of the powder. The CFD is used as a virtual test bed to determine thermal parameters such as density, heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to test the sensitivity of the melted zone and distortion using Structural Mechanics. Results showed significant influence of particle size distribution on the packing density, surface height, surface roughness, the stress state and displacement of the melted zone. The results will serve as a catalyst in developing geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.
Multiphase flow simulation using Smoothed Particle Hydrodynamics (SPH) has gained interest during... more Multiphase flow simulation using Smoothed Particle Hydrodynamics (SPH) has gained interest during recent years, mostly due to the inherent flexibility of the method and the physically rather intuitive formulation of extra constitutive equations needed when dealing with for instance non-Newtonian flows. In the work presented here, simulations based on an SPH model implemented in the flow solver IBOFlow has been used for simulation of robotic application of sealing material on a car body. Application of sealing materials is done in order to prevent water leakage into cavities of the body, and to reduce noise. In off-line programming of the robots in the automotive paintshop it is of great interest to predict shape and appearance of sealing material without having to resort to trial and error procedures. The flow of sealing material in the air between applicator and target (car body) is relatively uncomplicated, as the material mostly moves at constant velocity until impact on target. ...
Heat transfer modeling of large industrial ovens such as those used in automotive paintshops is d... more Heat transfer modeling of large industrial ovens such as those used in automotive paintshops is difficult due to the large and multiple scales and long curing times. The flow inside a convective oven is turbulent, and the process includes large temperature gradients. An efficient simulation requires a simplified and localized model of the heat transfer coupling. We present a novel method with three ingredients: localization using local Nusselt numbers of the oven nozzles, projection of Nusselt number profiles onto the target, and efficient conduction modeling on a coarse background mesh. The approach, which was developed in a research project together with the Swedish automotive industry, makes it possible to accurately simulate a curing oven with close to real-time performance. The simulation results are demonstrated to be in close agreement with measurements from automotive production.
Purpose The purpose of this study is to propose a novel simulation framework and show that it cap... more Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by ...
Abstract The hydrodynamics around a Brownian particle has a noticeable impact on its hindered dif... more Abstract The hydrodynamics around a Brownian particle has a noticeable impact on its hindered diffusion in arbitrary geometries (such as channels/pores) due to reduced mobility close to walls. These effects are difficult to describe at sub-pore scales, wherein a complete analytical solution of the underlying hydrodynamics is challenging to obtain. Here, we propose a coupled Langevin-multiphase direct numerical simulation (DNS) framework, that fully resolves the hydrodynamics in such systems and consequently provides an on-the-fly capability to probe local instantaneous particle diffusivities. We validate and establish the capabilities of this framework in square micro-channels (under varying degrees of hydrodynamic confinement) and in an arbitrary pore. Our results show that directional variations in mean-squared displacements, velocity auto-correlation functions and diffusivities of the Brownian particle, due to inherent asymmetries in the geometry are adequately captured. Further, a local anisotropy in the hydrodynamic resistances along the co-axial direction of the channel is also noted.
Oven curing of automotive parts is a complex industrial process involving multiple scales ranging... more Oven curing of automotive parts is a complex industrial process involving multiple scales ranging from submillimeter thick layers to the size of the ovens, and long curing times. In this work, the process is simulated by state-of-the-art immersed boundary techniques. First, the simulations are validated against temperature measurements, in a lab scale oven, of three parts taken from a truck cab. Second, a novel multicriteria optimization method is proposed. It is applied to study the optimal positioning of the three parts with respect to curing time and energy consumption. The results presented demonstrate that complex industrial heat transfer processes can be optimized by combining state-of-the-art simulation technology and deterministic optimization techniques.
In this paper a novel method is proposed, where a constitutive equation for the viscoelastic stre... more In this paper a novel method is proposed, where a constitutive equation for the viscoelastic stress is solved in a Lagrangian frame of reference, and the full stress tensor is interpolated to the Eulerian fluid grid. The method is validated for a 2D flow past a confined cylinder and used to simulate the 3D multiphase flow of adhesive application.
We present a simulation framework that makes it possible to accurately simulate spray painting of... more We present a simulation framework that makes it possible to accurately simulate spray painting of e.g. a truck cab in only a few hours on a standard computer. This is an extreme improvement compared to earlier approaches that require weeks of simulation time. Unique algorithms for coupled simulations of air flows, electrostatic fields and charged paint particles make this possible. In addition, we demonstrate that the same framework can be used to efficiently simulate the laydown of sealing or adhesive material. In the virtual paint factory the production preparation process can be performed in the computer, which allows the engineers to replace physical prototypes with virtual ones to shorten the lead time in product development, and avoid future unforeseen technological and environmental problems that can be extremely costly if they are discovered at the end of the production line, or even worse by the costumer.
In the last decades, the biomedical relevance of mathematical models has been demonstrated and co... more In the last decades, the biomedical relevance of mathematical models has been demonstrated and comparison of experiments against computer simulations has been encouraged. Blood circulation in the human liver and in particular perfusion, the process of delivering blood to the capillary bed, is an open problem and inherently multiscale in nature. Models currently available in the literature [2, 1] either present a macroscale approach in which liver is assumed as a homogeneous anisotropic porous medium and therefore flow within it is simulated using Darcy’s equation, or they work at the microscale where the vascular and extravascular domains need to be treated differently solving Stokes’ equation in the former and Darcy’s equation in the latter and applying suitable coupling condition at the interface. In this communication, instead, we present an approach where the Darcy-Stokes-Brinkmann [3] equation is used on the entire computational domain, different areas of the tissue being repre...
Computer simulations are important to increase the knowledge of the processes involved in paper m... more Computer simulations are important to increase the knowledge of the processes involved in paper making. Because of the complexity of the paper processes the development of simulation tools requires models and numerical methods which capture as much as possible of the real physical phenomena. In this paper a framework for simulation of fiber suspension flow is presented. The framework is founded on a fluid solver for the Navier-Stokes equations and a fiber model based on finite strain beam theory including shearing. Moreover, the coupling between fibers and fluid is resolved with the immersed boundary method and the interaction between the fibers is calculated using a model based on DLVO-theory.
Selective laser melting process is a powder bed fusion additive manufacturing process that finds ... more Selective laser melting process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the end product. This paper investigates the effect of PSD on deformation for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder distribution based on the different particle size distribution of the powder. The CFD is used as a virtual test bed to determine thermal parameters such as density, heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to test the sensitivity of the melted zone and distortion using Structural Mechanics. Results showed significant influence of particle size distribution on the packing density, surface height, surface roughness, the stress state and displacement of the melted zone. The results will serve as a catalyst in developing geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.
Multiphase flow simulation using Smoothed Particle Hydrodynamics (SPH) has gained interest during... more Multiphase flow simulation using Smoothed Particle Hydrodynamics (SPH) has gained interest during recent years, mostly due to the inherent flexibility of the method and the physically rather intuitive formulation of extra constitutive equations needed when dealing with for instance non-Newtonian flows. In the work presented here, simulations based on an SPH model implemented in the flow solver IBOFlow has been used for simulation of robotic application of sealing material on a car body. Application of sealing materials is done in order to prevent water leakage into cavities of the body, and to reduce noise. In off-line programming of the robots in the automotive paintshop it is of great interest to predict shape and appearance of sealing material without having to resort to trial and error procedures. The flow of sealing material in the air between applicator and target (car body) is relatively uncomplicated, as the material mostly moves at constant velocity until impact on target. ...
Heat transfer modeling of large industrial ovens such as those used in automotive paintshops is d... more Heat transfer modeling of large industrial ovens such as those used in automotive paintshops is difficult due to the large and multiple scales and long curing times. The flow inside a convective oven is turbulent, and the process includes large temperature gradients. An efficient simulation requires a simplified and localized model of the heat transfer coupling. We present a novel method with three ingredients: localization using local Nusselt numbers of the oven nozzles, projection of Nusselt number profiles onto the target, and efficient conduction modeling on a coarse background mesh. The approach, which was developed in a research project together with the Swedish automotive industry, makes it possible to accurately simulate a curing oven with close to real-time performance. The simulation results are demonstrated to be in close agreement with measurements from automotive production.
Purpose The purpose of this study is to propose a novel simulation framework and show that it cap... more Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by ...
Abstract The hydrodynamics around a Brownian particle has a noticeable impact on its hindered dif... more Abstract The hydrodynamics around a Brownian particle has a noticeable impact on its hindered diffusion in arbitrary geometries (such as channels/pores) due to reduced mobility close to walls. These effects are difficult to describe at sub-pore scales, wherein a complete analytical solution of the underlying hydrodynamics is challenging to obtain. Here, we propose a coupled Langevin-multiphase direct numerical simulation (DNS) framework, that fully resolves the hydrodynamics in such systems and consequently provides an on-the-fly capability to probe local instantaneous particle diffusivities. We validate and establish the capabilities of this framework in square micro-channels (under varying degrees of hydrodynamic confinement) and in an arbitrary pore. Our results show that directional variations in mean-squared displacements, velocity auto-correlation functions and diffusivities of the Brownian particle, due to inherent asymmetries in the geometry are adequately captured. Further, a local anisotropy in the hydrodynamic resistances along the co-axial direction of the channel is also noted.
Oven curing of automotive parts is a complex industrial process involving multiple scales ranging... more Oven curing of automotive parts is a complex industrial process involving multiple scales ranging from submillimeter thick layers to the size of the ovens, and long curing times. In this work, the process is simulated by state-of-the-art immersed boundary techniques. First, the simulations are validated against temperature measurements, in a lab scale oven, of three parts taken from a truck cab. Second, a novel multicriteria optimization method is proposed. It is applied to study the optimal positioning of the three parts with respect to curing time and energy consumption. The results presented demonstrate that complex industrial heat transfer processes can be optimized by combining state-of-the-art simulation technology and deterministic optimization techniques.
In this paper a novel method is proposed, where a constitutive equation for the viscoelastic stre... more In this paper a novel method is proposed, where a constitutive equation for the viscoelastic stress is solved in a Lagrangian frame of reference, and the full stress tensor is interpolated to the Eulerian fluid grid. The method is validated for a 2D flow past a confined cylinder and used to simulate the 3D multiphase flow of adhesive application.
We present a simulation framework that makes it possible to accurately simulate spray painting of... more We present a simulation framework that makes it possible to accurately simulate spray painting of e.g. a truck cab in only a few hours on a standard computer. This is an extreme improvement compared to earlier approaches that require weeks of simulation time. Unique algorithms for coupled simulations of air flows, electrostatic fields and charged paint particles make this possible. In addition, we demonstrate that the same framework can be used to efficiently simulate the laydown of sealing or adhesive material. In the virtual paint factory the production preparation process can be performed in the computer, which allows the engineers to replace physical prototypes with virtual ones to shorten the lead time in product development, and avoid future unforeseen technological and environmental problems that can be extremely costly if they are discovered at the end of the production line, or even worse by the costumer.
In the last decades, the biomedical relevance of mathematical models has been demonstrated and co... more In the last decades, the biomedical relevance of mathematical models has been demonstrated and comparison of experiments against computer simulations has been encouraged. Blood circulation in the human liver and in particular perfusion, the process of delivering blood to the capillary bed, is an open problem and inherently multiscale in nature. Models currently available in the literature [2, 1] either present a macroscale approach in which liver is assumed as a homogeneous anisotropic porous medium and therefore flow within it is simulated using Darcy’s equation, or they work at the microscale where the vascular and extravascular domains need to be treated differently solving Stokes’ equation in the former and Darcy’s equation in the latter and applying suitable coupling condition at the interface. In this communication, instead, we present an approach where the Darcy-Stokes-Brinkmann [3] equation is used on the entire computational domain, different areas of the tissue being repre...
Computer simulations are important to increase the knowledge of the processes involved in paper m... more Computer simulations are important to increase the knowledge of the processes involved in paper making. Because of the complexity of the paper processes the development of simulation tools requires models and numerical methods which capture as much as possible of the real physical phenomena. In this paper a framework for simulation of fiber suspension flow is presented. The framework is founded on a fluid solver for the Navier-Stokes equations and a fiber model based on finite strain beam theory including shearing. Moreover, the coupling between fibers and fluid is resolved with the immersed boundary method and the interaction between the fibers is calculated using a model based on DLVO-theory.
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