ABSTRACT Optimum design of structures has been traditionally focused on the analysis of shape and... more ABSTRACT Optimum design of structures has been traditionally focused on the analysis of shape and dimensions optimization problems. However, more recently a new discipline has emerged: the topology optimization of the structures. This discipline states innovative models that allow to obtain optimal solutions without a previous definition of the type of structure being considered. These formulations obtain the optimal topology and the optimal shape and size of the resulting elements. The most usual formulations of the topology optimization problem try to obtain the structure of maximum stiffness. These approaches maximize the stiffness for a given amount of material to be used. These formulations have been widely analyzed and applied in engineering but they present considerable drawbacks from a numerical and from a practical point of view. In this paper the author propose a different formulation, as an alternative to maximum stiffness approaches, that minimizes the weight and includes stress constraints. The advantages of this kind of formulations are crucial since the cost of the structure is minimized, which is the most frequent objective in engineering, and they guarantee the structural feasibility since stresses are constrained. In addition, this approach allows to avoid some of the drawbacks and numerical instabilities related to maximum stiffness approaches. Finally, some practical examples have been solved in order to verify the validity of the results obtained and the advantages of the proposed formulation.
IOP Conference Series: Materials Science and Engineering, 2010
ABSTRACT The design of safe grounding systems in electrical installations is essential to assure ... more ABSTRACT The design of safe grounding systems in electrical installations is essential to assure the protection of the equipment, the power supply continuity and the security of the persons. In order to achieve these goals, it is necessary to compute the equivalent electrical resistance of the system and the potential distribution on the earth surface when a fault condition occurs. In the last years the authors have developed a numerical formulation based on the BEM for the analysis of grounding systems embedded in uniform and layered soils. As it is known, in practical cases the underlying series have a poor rate of convergence and the use of multilayer soils requires an out of range computational cost. In this paper we present an efficient technique based on the Aitken δ2-process in order to improve the rate of convergence of the involved series expansions.
ABSTRACT Minimum weight formulations with stress constraints have been recently proposed as an al... more ABSTRACT Minimum weight formulations with stress constraints have been recently proposed as an alternative to the traditional maximum stiffness statements for the topology optimization of structures. These minimum weight approaches offer some advantages and avoid unwanted phenomena associated to maximum stiffness approaches, e.g. mesh dependency, checkerboard layouts. In addition, minimum weight formulations analyze more usual statements from a practical point of view in engineering since they reduce the cost of the structure and impose stress constraints. The minimum weight formulation with stress constraints proposed in this paper guarantees the feasibility of the optimal solutions obtained while the cost is minimized.However, these formulations also require bigger computing effort than the traditional maximum stiffness statements since the number of highly non-linear stress constraints is drastically increased while the number of design variables is analogous. Thus, it is necessary to introduce numerical methods and computational techniques that allow to reduce the resources required.In this paper, we propose the use of parallelization techniques in order to reduce the computing time required to solve the topology optimization problem with stress constraints proposed.
... approach. For this reason, we will introduce a more suitable class of global type constraints... more ... approach. For this reason, we will introduce a more suitable class of global type constraints by grouping the elements into blocks. 5. Block aggregated statement of stress constraints. Let us ... cost. 5.1. Block definition. The correct ...
In this paper we focus on the application of a higher-order finite volume method for the resoluti... more In this paper we focus on the application of a higher-order finite volume method for the resolution of Computational Aeroacoustics problems. In particular, we present the application of a finite volume method based in Moving Least Squares approximations in the context of a hybrid approach for low Mach number flows. In this case, the acoustic and aerodynamic fields can be computed separately. We focus on two kinds of computations: turbulent flow and aeroacoustics in complex geometries. Both fields require very accurate methods to capture the fine features of the flow, small scales in the case of turbulent flows and very low-amplitude acoustic waves in the case of aeroacoustics. On the other hand, the use of unstructured grids is interesting for real engineering applications, but unfortunately, the accuracy and efficiency of the numerical methods developed for unstructured grids is far to reach the performance of those methods developed for structured grids. In this context, we propose the FV-MLS method as a tool for accurate CAA computations on unstructured grids.
ABSTRACT Optimum design of structures has been traditionally focused on the analysis of shape and... more ABSTRACT Optimum design of structures has been traditionally focused on the analysis of shape and dimensions optimization problems. However, more recently a new discipline has emerged: the topology optimization of the structures. This discipline states innovative models that allow to obtain optimal solutions without a previous definition of the type of structure being considered. These formulations obtain the optimal topology and the optimal shape and size of the resulting elements. The most usual formulations of the topology optimization problem try to obtain the structure of maximum stiffness. These approaches maximize the stiffness for a given amount of material to be used. These formulations have been widely analyzed and applied in engineering but they present considerable drawbacks from a numerical and from a practical point of view. In this paper the author propose a different formulation, as an alternative to maximum stiffness approaches, that minimizes the weight and includes stress constraints. The advantages of this kind of formulations are crucial since the cost of the structure is minimized, which is the most frequent objective in engineering, and they guarantee the structural feasibility since stresses are constrained. In addition, this approach allows to avoid some of the drawbacks and numerical instabilities related to maximum stiffness approaches. Finally, some practical examples have been solved in order to verify the validity of the results obtained and the advantages of the proposed formulation.
IOP Conference Series: Materials Science and Engineering, 2010
ABSTRACT The design of safe grounding systems in electrical installations is essential to assure ... more ABSTRACT The design of safe grounding systems in electrical installations is essential to assure the protection of the equipment, the power supply continuity and the security of the persons. In order to achieve these goals, it is necessary to compute the equivalent electrical resistance of the system and the potential distribution on the earth surface when a fault condition occurs. In the last years the authors have developed a numerical formulation based on the BEM for the analysis of grounding systems embedded in uniform and layered soils. As it is known, in practical cases the underlying series have a poor rate of convergence and the use of multilayer soils requires an out of range computational cost. In this paper we present an efficient technique based on the Aitken δ2-process in order to improve the rate of convergence of the involved series expansions.
ABSTRACT Minimum weight formulations with stress constraints have been recently proposed as an al... more ABSTRACT Minimum weight formulations with stress constraints have been recently proposed as an alternative to the traditional maximum stiffness statements for the topology optimization of structures. These minimum weight approaches offer some advantages and avoid unwanted phenomena associated to maximum stiffness approaches, e.g. mesh dependency, checkerboard layouts. In addition, minimum weight formulations analyze more usual statements from a practical point of view in engineering since they reduce the cost of the structure and impose stress constraints. The minimum weight formulation with stress constraints proposed in this paper guarantees the feasibility of the optimal solutions obtained while the cost is minimized.However, these formulations also require bigger computing effort than the traditional maximum stiffness statements since the number of highly non-linear stress constraints is drastically increased while the number of design variables is analogous. Thus, it is necessary to introduce numerical methods and computational techniques that allow to reduce the resources required.In this paper, we propose the use of parallelization techniques in order to reduce the computing time required to solve the topology optimization problem with stress constraints proposed.
... approach. For this reason, we will introduce a more suitable class of global type constraints... more ... approach. For this reason, we will introduce a more suitable class of global type constraints by grouping the elements into blocks. 5. Block aggregated statement of stress constraints. Let us ... cost. 5.1. Block definition. The correct ...
In this paper we focus on the application of a higher-order finite volume method for the resoluti... more In this paper we focus on the application of a higher-order finite volume method for the resolution of Computational Aeroacoustics problems. In particular, we present the application of a finite volume method based in Moving Least Squares approximations in the context of a hybrid approach for low Mach number flows. In this case, the acoustic and aerodynamic fields can be computed separately. We focus on two kinds of computations: turbulent flow and aeroacoustics in complex geometries. Both fields require very accurate methods to capture the fine features of the flow, small scales in the case of turbulent flows and very low-amplitude acoustic waves in the case of aeroacoustics. On the other hand, the use of unstructured grids is interesting for real engineering applications, but unfortunately, the accuracy and efficiency of the numerical methods developed for unstructured grids is far to reach the performance of those methods developed for structured grids. In this context, we propose the FV-MLS method as a tool for accurate CAA computations on unstructured grids.
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