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Most computational fluid dynamics (CFD) modelling of material extrusion additive manufacturing (MEX-AM) mainly relies on a moving boundary condition applied to the print bed and not the direct modelling of the motion of the nozzle. This paper presents step-by-step and detailed implementation of the nozzle motion as well as non-isothermal non-Newtonian flow during MEX-AM in Ansys Fluent. For nozzle motion the overset approach is used for the meshing which allows for the nozzle and the rest of the domain to be meshes separately, streamlining meshing and motion. The method is initially used to simulate a single strand, which was validated against experimental and numerical data. It was then applied to demonstrate out-of-plane nozzle motion in two case studies: three-layer printing and printing on a ramp. The model is further developed to simulate a single strand deposition with the well-known Cross–William–Landel–Ferry (Cross-WLF) behaviour for a thermal and shear-dependent material flow.

This paper presents a comparison of experimental and numerical modelling results of the velocity field around a fume cupboard with a static and a dynamic mesh. During fume cupboard testing, components are required to move which mimic typical operating conditions, the amount of tracer gas released is then measured. This tracer gas is harmful to the environment and so an alternative is required. Advanced Computational Fluid Dynamics (CFD) techniques, such as dynamic meshing, have been utilised to replicate aspects of the current tests. The fume cupboard was tested in normal operating conditions and under the influence of a board inducing a wake close to the fume cupboard entrance. The velocity fields have been compared and show a reasonable level of accuracy with a percentage difference between experimental and simulated results of around 5% using both a static and a dynamic domain. This is an improvement on the 15–20% accuracy for detecting concentration of tracer gas using previous experimental methods. The aim of this work is to satisfy the scientific community and fume cupboard operators that CFD is sufficiently accurate to assess fume cupboard performance under real world scenarios. [ABSTRACT FROM AUTHOR]

Most computational fluid dynamics (CFD) modelling of material extrusion additive manufacturing (MEX-AM) mainly relies on a moving boundary condition applied to the print bed and not the direct modelling of the motion of the nozzle. This paper presents step-by-step and detailed implementation of the nozzle motion as well as non-isothermal non-Newtonian flow during MEX-AM in Ansys Fluent. For nozzle motion the overset approach is used for the meshing which allows for the nozzle and the rest of the domain to be meshes separately, streamlining meshing and motion. The method is initially used to simulate a single strand, which was validated against experimental and numerical data. It was then applied to demonstrate out-of-plane nozzle motion in two case studies: three-layer printing and printing on a ramp. The model is further developed to simulate a single strand deposition with the well-known Cross–William–Landel–Ferry (Cross-WLF) behaviour for a thermal and shear-dependent material flow. [ABSTRACT FROM AUTHOR]

The geometric complexity and high-pressure gradients that characterize the design of the flow field of gear pumps make it very difficult to obtain an accurate CFD simulation of the component. Usually, assumptions are made both in terms of geometrical features and physics being included in the analysis. The contact between the teeth, which is a key factor for the correct functioning of these pumps, represents a critical challenge in 3D CFD simulations, mainly due to the intrinsic limits of the dynamic meshing techniques that can hardly effectively manage a zero or close to zero gap point forming during gear rotation. The geometric complexity and high-pressure gradients that characterize the gear pump flow field make a CFD analysis quite difficult, and the contact between the gear teeth is usually avoided, thus being an extremely important feature. In this paper, a gear pump composed of inlet and outlet pipes was considered, and the contact between the gear's teeth was modeled in two different ways, one where it is effectively implemented and one where it is avoided using distancing and a proper casing modification. Herein, a new methodology is proposed for the application of the dynamic mesh method in the Simcenter STAR-CCM+ environment using an adaptive remeshing technique. The proposed methodology is compared with the alternative overset meshing method available in the software. The new meshing method is implemented using a user-routing that reproduces the real geometry of the gears while rotating during the pump operation, with teeth contact included. The routine is optimized in order to limit the additional computation and time needed for the remeshing process. The results that can be obtained using the two meshing approaches for the gear pump are compared in terms of computational effort and the accuracy of the results. The two methods showed opposite results in almost all the reported results, with the overset being more precise in the radial pressure evaluation and the dynamic being more reliable in the cavitation/aeration extension cloud. [ABSTRACT FROM AUTHOR]

The geometric complexity and high-pressure gradients that characterize the design of the flow field of gear pumps make it very difficult to obtain an accurate CFD simulation of the component. Usually, assumptions are made both in terms of geometrical features and physics being included in the analysis. The contact between the teeth, which is a key factor for the correct functioning of these pumps, represents a critical challenge in 3D CFD simulations, mainly due to the intrinsic limits of the dynamic meshing techniques that can hardly effectively manage a zero or close to zero gap point forming during gear rotation. The geometric complexity and high-pressure gradients that characterize the gear pump flow field make a CFD analysis quite difficult, and the contact between the gear teeth is usually avoided, thus being an extremely important feature. In this paper, a gear pump composed of inlet and outlet pipes was considered, and the contact between the gear’s teeth was modeled in two different ways, one where it is effectively implemented and one where it is avoided using distancing and a proper casing modification. Herein, a new methodology is proposed for the application of the dynamic mesh method in the Simcenter STAR-CCM+ environment using an adaptive remeshing technique. The proposed methodology is compared with the alternative overset meshing method available in the software. The new meshing method is implemented using a user-routing that reproduces the real geometry of the gears while rotating during the pump operation, with teeth contact included. The routine is optimized in order to limit the additional computation and time needed for the remeshing process. The results that can be obtained using the two meshing approaches for the gear pump are compared in terms of computational effort and the accuracy of the results. The two methods showed opposite results in almost all the reported results, with the overset being more precise in the radial pressure evaluation and the dynamic being more reliable in the cavitation/aeration extension cloud.