Heat Transport through Rough Channels

We investigate the two-dimensional transport of heat through viscous flow between two parallel rough interfaces with a given fractal geometry. The flow and heat transport equations are solved through direct numerical simulations, and for different conduction-convection conditions. Compared with the behavior of a channel with smooth interfaces, the results for the rough channel at low and moderate values of the Peclet number indicate that the effect of roughness is almost negligible on the efficiency of the heat transport system. This is explained here in terms of the Makarov's theorem, using the notion of active zone in Laplacian transport. At sufficiently high Peclet numbers, where convection becomes the dominant mechanism of heat transport, the role of the interface roughness is to generally increase both the heat flux across the wall as well as the active length of heat exchange, when compared with the smooth channel. Finally, we show that this last behavior is closely related with the presence of recirculation zones in the reentrant regions of the fractal geometry.Comment: 12 pages, 8 figure

Experimental and numerical vibration correlation of pre-stressed laminated reinforced panel

This research work deals with the buckling load prediction of reinforced laminated composite panels of aeronautical interest. Being subjected to pure compression, these panels are characterized by stable post-buckling. Thus, the vibration correlation technique (VCT) is utilized herein as an effective nondestructive means to extrapolate critical loads from free vibration measurements. A hierarchical design of experiments, making use of nested multifactors (i.e. panel replicas, test setups, and measurement repetitions), is employed to estimate components of variance. The experimental outcomes are compared with the results of an advanced finite element model with layer-wise kinematics and based on the Carrera Unified Formulation (CUF). The results show that, although obtained with a low number of tests and specimens, the VCT experiments are repeatable and provide a good validation of the numerical simulations, which are demonstrated to be accurate and reliable.</p

Buckling test of stiffened panels: modeling and vibrational correlation testing

Representative stiffened panels are optimized such that multiple buckling modes and failure (using open hole allowables) occur within a range of 10% of the lowest buckling load. This implies the panels cannot be loaded up to the buckling load without risking failure, hence vibrational correlation testing was used to estimate the buckling loads and modes. At the same time, a finite element model was created using the Carrera Unified Formulation. This model was validated using the tests and a good correlation between both was observed. Three panels were manufactured and each panel was put in place for testing twice. Each time a panel was put in place, the test was repeated three times. This allowed us to get a ballpark estimate for the variation due to replicas of the panel, the test set-up and repeating the tests.Aerospace Structures & Computational Mechanic

Buckling test of stiffened panels: Modeling and vibrational correlation testing

Representative stiffened panels are optimized such that multiple buckling modes and failure (using open hole allowables) occur within a range of 10% of the lowest buckling load. This implies the panels cannot be loaded up to the buckling load without risking failure, hence vibrational correlation testing was used to estimate the buckling loads and modes. At the same time, a finite element model was created using the Carrera Unified Formulation. This model was validated using the tests and a good correlation between both was observed. Three panels were manufactured and each panel was put in place for testing twice. Each time a panel was put in place, the test was repeated three times. This allowed us to get a ballpark estimate for the variation due to replicas of the panel, the test set-up and repeating the tests

Buckling test of stiffened panels: Modeling and vibrational correlation testing

Representative stiffened panels are optimized such that multiple buckling modes and failure (using open hole allowables) occur within a range of 10% of the lowest buckling load. This implies the panels cannot be loaded up to the buckling load without risking failure, hence vibrational correlation testing was used to estimate the buckling loads and modes. At the same time, a finite element model was created using the Carrera Unified Formulation. This model was validated using the tests and a good correlation between both was observed. Three panels were manufactured and each panel was put in place for testing twice. Each time a panel was put in place, the test was repeated three times. This allowed us to get a ballpark estimate for the variation due to replicas of the panel, the test set-up and repeating the tests.Aerospace Structures & Computational Mechanic

Buckling test of stiffened panels: evaluation of post-buckling and failure by testing and layerwise models

The present paper deals with the buckling and post-buckling analysis of a multilayered composite reinforced panel. The panel, designed for aeronautical applications, results in a complex stacking sequence, and the development of a refined model able to describe its geometrical nonlinear behavior is mandatory to avoid the usage of highly computational effortrequired 3D finite elements. The proposed approach is a finite element analysis based on the Carrera Unified Formulation (CUF). Thanks to CUF, a 1D model of the composite panel can be formulated and complicated stress fields within the structure can be evaluated, so that the nonlinear behavior is fully described. A refined Equivalent Single Layer (ESL) technique is employed, making use of Lagrange polynomials for the description of the stacking sequence. The results clearly demonstrate the reliability of this approach, comparing the linearized buckling and nonlinear post-buckling solutions with those from Nastran (1D, 2D and 3D) and experiment

Buckling test of stiffened panels: Evaluation of post-buckling and failure by testing and layerwise models

The present paper deals with the buckling and post-buckling analysis of a multilayered composite reinforced panel. The panel, design for aeronautical applications, results in a complex stacking sequence, and the development of a refined model able to describe its geometrical nonlinear behavior is mandatory to avoid the usage of highly computational effort-required 3D finite elements. The proposed approach is a finite element analysis based on the Carrera Unified Formulation (CUF). Thanks to CUF, a 1D model of the composite panel can be formulated and complicated stress fields within the structure can be evaluated, so the nonlinear behavior is fully described. A refined Equivalent Single Layer (ESL) technique is employed, making use of Lagrange polynomials for the description of the stacking sequence. The results clearly demonstrate the reliability of this approach, comparing the linearized buckling and nonlinear post-buckling solutions with those from Nastran (1D, 2D and 3D) and experiments

Experimental and numerical vibration correlation of pre-stressed laminated reinforced panel

This research work deals with the buckling load prediction of reinforced laminated composite panels of aeronautical interest. Being subjected to pure compression, these panels are characterized by stable post-buckling. Thus, the vibration correlation technique (VCT) is utilized herein as an effective nondestructive means to extrapolate critical loads from free vibration measurements. A hierarchical design of experiments, making use of nested multifactors (i.e. panel replicas, test setups, and measurement repetitions), is employed to estimate components of variance. The experimental outcomes are compared with the results of an advanced finite element model with layer-wise kinematics and based on the Carrera Unified Formulation (CUF). The results show that, although obtained with a low number of tests and specimens, the VCT experiments are repeatable and provide a good validation of the numerical simulations, which are demonstrated to be accurate and reliable.Aerospace Structures & Computational Mechanic

Buckling test of stiffened panels: Evaluation of post-buckling and failure by testing and layerwise models

The present paper deals with the buckling and post-buckling analysis of a multilayered composite reinforced panel. The panel, design for aeronautical applications, results in a complex stacking sequence, and the development of a refined model able to describe its geometrical nonlinear behavior is mandatory to avoid the usage of highly computational effort-required 3D finite elements. The proposed approach is a finite element analysis based on the Carrera Unified Formulation (CUF). Thanks to CUF, a 1D model of the composite panel can be formulated and complicated stress fields within the structure can be evaluated, so the nonlinear behavior is fully described. A refined Equivalent Single Layer (ESL) technique is employed, making use of Lagrange polynomials for the description of the stacking sequence. The results clearly demonstrate the reliability of this approach, comparing the linearized buckling and nonlinear post-buckling solutions with those from Nastran (1D, 2D and 3D) and experiments.Aerospace Structures & Computational Mechanic