Philip Cardiff | University College Dublin (original) (raw)

Papers by Philip Cardiff

Computers in Biology and Medicine, Sep 1, 2023

The properties of intracranial aneurysms (IAs) walls are known to be driven by the underlying hem... more The properties of intracranial aneurysms (IAs) walls are known to be driven by the underlying hemodynamics adjacent to the IA sac. Different pathways exist explaining the connections between hemodynamics and local tissue properties. The emergence of such theories is essential if one wishes to compute the mechanical response of a patient-specific IA wall and predict its rupture. Apart from the hemodynamics and tissue properties, one could assume that the mechanical response also depends on the local morphology, more specifically, the wall curvature, with larger values at highly-curved wall portions. Nonetheless, this contradicts observations of IA rupture sites more often found at the dome, where the curvature is lower. This seeming contradiction indicates a complex interaction between local hemodynamics, wall morphology, and mechanical response, which warrants further investigation. This was the main goal of this work. We accomplished this by analysing the stress and stretch fields in different regions of the wall for a sample of IAs, which have been classified based on particular local hemodynamics and local curvature. Pulsatile numerical simulations were performed using the one-way fluid-solid interaction strategy implemented in OpenFOAM (solids4foam toolbox). We found that the variable best correlated with regions of high stress and stretch was the wall curvature. Additionally, our data suggest a connection between the local curvature and local hemodynamics, indicating that the curvature is a property that could be used to assess both mechanical response and hemodynamic conditions, and, moreover, to suggest new metrics based on the curvature to predict the likelihood of rupture.

As the overlap between traditional computational mechanics and machine learning grows, there is a... more As the overlap between traditional computational mechanics and machine learning grows, there is an increasing demand for straightforward approaches to interface Python-based procedures with C++-based OpenFOAM. This article introduces one such general methodology, allowing the execution of Python code directly within an OpenFOAM solver without the need for Python code translation. The proposed approach is based on the lightweight library pybind11, where OpenFOAM data is transferred to an embedded Python interpreter for manipulation, and results are returned as needed. Following a review of related approaches, the article describes the approach, with a particular focus on data transfer between Python and OpenFOAM, executing Python scripts and functions, and practical details about the implementation in OpenFOAM. Three complementary test cases are presented to highlight the functionality and demonstrate the effect of different data transfer approaches: a Python-based velocity profile boundary condition; a Python-based solver for prototyping; and a machine learning mechanical constitutive law class for solids4foam which performs field calculations.

50th U.S. Rock Mechanics/Geomechanics Symposium, Jun 26, 2016

Engineering Fracture Mechanics, Nov 1, 2018

This study presents recent achievements in understanding the fracture behaviour of rubbermodified... more This study presents recent achievements in understanding the fracture behaviour of rubbermodified epoxy adhesives, notably the determination of the fully developed fracture process zone (FPZ) and its associated intrinsic fracture energy, G 0. The shape and size of the FPZ are identified by inspecting the fracture surfaces using SEM, and exploring subsurface damage using optical microscopy and TEM. The thickness and failure strain of the FPZ are found to be essentially the same for different fracture tests, i.e. tapered double cantilever beam and single edge notched bending tests. As a consequence, the results from different fracture tests are linked by using the geometrically transferable, true fracture properties, i.e. FPZ thickness and G 0. The variation of total fracture energy observed in different fracture tests is attributed to varying plastic deformation energy dissipated in plastic deformation zone (outside FPZ). The fracture behaviour of the adhesive is then successfully predicted by a cohesive zone model using parameters extracted from experiments.

Wind actions can have a great impact on both bridges and traffic on bridges. However, structures ... more Wind actions can have a great impact on both bridges and traffic on bridges. However, structures designed to shelter the traffic from wind can influence the aerodynamic performance of the bridge deck, especially for long-span bridges. This study compares the effect of non-perforated walls and perforated walls used as wind barriers for traffic by conducting Computational Fluid Dynamics (CFD) simulations on three-dimensional geometries of a four-lane bridge deck. Steady-state simulations employ the Reynolds-Averaged Navier Stokes (RANS) method with the k-epsilon turbulence model and all simulations use parallel computing. An open-sourced software OpenFOAM is used.

Springer eBooks, 2014

Traditional CAD tools generate a static solution to a design problem. Parametric systems allow th... more Traditional CAD tools generate a static solution to a design problem. Parametric systems allow the user to explore many variations on that design theme. Such systems make the computer a generative design tool and are already used extensively as a rapid prototyping technique in architecture and aeronautics. Combining a design generation tool with an evolutionary algorithm provides a methodology for optimising designs. This works uses NASA's parametric aircraft design tool (OpenVSP) and an evolutionary algorithm to evolve a range of aircraft that maximise lift and reduce drag while remaining within the framework of the original design. Our approach allows the designer to automatically optimise their chosen design and to generate models with improved aerodynamic efficiency.

50th U.S. Rock Mechanics/Geomechanics Symposium, Jun 26, 2016

Polymers, Dec 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Archives of Computational Methods in Engineering, Feb 2, 2021

Since early publications in the late 1980s and early 1990s, the finite volume method has been sho... more Since early publications in the late 1980s and early 1990s, the finite volume method has been shown suitable for solid mechanics analyses. At present, there are several flavours of the method, which can be classified in a variety of ways, such as grid arrangement (cell-centred vs staggered vs vertex-centred), solution algorithm (implicit vs explicit), and stabilisation strategy (Rhie-Chow vs Jameson-Schmidt-Turkel vs Godunov upwinding). This article gives an overview, historical perspective, comparison and critical analysis of the different approaches where a close comparison with the de facto standard for computational solid mechanics, the finite element method, is given. The article finishes with a look towards future research directions and steps required for finite volume solid mechanics to achieve more widespread acceptance.

Ocean Engineering, Jun 1, 2019

With global warming, the ice-covered areas in the Arctic are being transformed into open water. T... more With global warming, the ice-covered areas in the Arctic are being transformed into open water. This provides increased impetus for extensive maritime activities and attracts research interests in sea ice modelling. In the polar region, ice sheets can be several kilometres long and subjected to the effects of ocean waves. As its thickness to length ratio is very small, the wave response of such a large ice sheet, known as its hydroelastic response, is dominated by an elastic deformation rather than rigid body motions. In the past 25 years, sea ice hydroelasticity has been widely studied by theoretical models; however, recent experiments indicate that the ideal assumptions used for these theoretical models can cause considerable inaccuracies. This work proposes a numerical approach based on OpenFOAM to simulate the hydroelastic wave-ice interaction, with the Navier-Stokes equations describing the fluid domain, the St. Venant Kirchhoff solid model governing the ice deformation and a coupling scheme to achieve the fluid-structure interaction. Following validation against experiments, the proposed model has been shown capable of capturing phenomena that have not been included in current theoretical models. In particular, the developed model shows the capability to predict overwash, which is a ubiquitous polar phenomenon reported to be a key gap. The present model has the potential to be used to study wave-ice behaviours and the coupled wave-ice effect on marine structures.

This study used computational fluid dynamics (CFD) study to investigate the impact of helicopter ... more This study used computational fluid dynamics (CFD) study to investigate the impact of helicopter downwash on pedestrian comfort. The initial stage of the study involves the development of a helicopter downwash model that was compared to experimental values which showed some degree of coherence with areas situated downstream of the helicopter rotor. The initial stage was used to find suitable modelling parameters and an adequate resolution of computational mesh to produce a reliable helicopter downwash model. The final stage of the study is to integrate a helicopter in a built environment and assess the impact of downwash on pedestrian comfort. The concluding stage of the study showed that helicopter downwash effects can impose discomforting conditions in the immediate vicinity of the helicopter along with some minute propagating effects further downstream. Although its magnitude is smaller compared to effects of prevailing wind a local mitigation must be separately planned to deal with the effects of helicopter downwash.

SPE production & operations, Dec 14, 2017

Increasing the efficiency of completions in horizontal wells is an important concern in the oil a... more Increasing the efficiency of completions in horizontal wells is an important concern in the oil and gas industry. To decrease the number of fracturing stages per well, it is common practice to use multiple clusters per stage. This is done with the hope that most of the clusters in the stage will be effectively stimulated. Diagnostic evidence, however, suggests that in many cases, only one or two out of four or five clusters in a stage are effectively stimulated. In this paper, strategies to maximize the number of effectively stimulated perforation clusters are discussed. A fully 3D poroelastic model that simulates the propagation of nonplanar fractures in heterogeneous media is developed and used to model the propagation of multiple competing fractures. A parametric study is first conducted to demonstrate how important fracture-design variables, such as limited-entry perforations and cluster spacing, and formation parameters, such as permeability and lateral and vertical heterogeneity, affect the growth of competing fractures. The effect of stress shadowing caused by both mechanical and poroelastic effects is accounted for. 3D numerical simulations have been performed to show the effect of some operational and reservoir parameters on simultaneouscompetitive-fracture propagation. It was found that an increase in stage spacing decreases the stress interference between propagating fractures and increases the number of propagating fractures in a stage. It was also found that an increase in reservoir permeability can decrease the stress interference between propagating fractures because of poroelastic-stress changes. A modest (approximately 25%) variability in reservoir mechanical properties along the wellbore is shown to be enough to alter the number of fractures created in a hydraulic-fracturing stage and mask the effects of stress shadowing. Interstage fracture simulations show post-shut-in fracture extension induced by stress interference from adjacent propagating fractures. The effect of poroelasticity is highlighted for infill-well-fracture design, and preferential fracture propagation toward depleted regions is clearly observed in multiwell-pad-fracture simulations. The results in this paper attempt to provide practitioners with a better understanding of multicluster-fracturing dynamics. On the basis of these findings, recommendations are made on how best to design fracture treatments that will lead to the successful placement of fluid and proppant in a single fracture, and result in a set of fractures that are competing for growth. The ability to successfully stimulate all perforation clusters is shown to be a function of key fracture-design parameters. Prior experimental work has also clearly shown that the perforation-cluster spacing influences the fracture-growth pattern. When closely spaced multiple fractures were propagated simultaneously, some fractures were much larger than others (El-Rabaa 1982; Abass et al. 1996). It was shown that in some cases, one fracture could become the dominant fracture propagating among the clusters. Bunger et al. (2012) used an analytical model and performed a dimensional analysis to understand the most-important parameters that need to be addressed when optimizing multiple-fracture-growth problems. They considered the deflection patterns that are generated because of interaction of the fractures with existing fractures. They applied their model to a 2D fracture-growth simulator. In a later paper, the Bunger et al. (2012) model was used to understand the effect of viscosity and toughness-dominated regimes on multiple-fracture propagation (Ames and Bunger 2015). The latter used a mathematical model to couple the contributions of fluid flow, rock breakage, and perforation pressure drop to the total power requirement for the growth of multiple hydraulic fractures. Their model predicts that when the stage spacing is less than the created fracture height, the probability of multiple-fracture growth is small. The fundamental understanding their model provides can be very useful in explaining observations from numerical models. Many researchers have used the displacement-discontinuity method to model the stress interference created by hydraulic fractures. Using this method, researchers have attempted to analyze the effect of simultaneous-multiple-fracture growth (

Neurocomputing, Oct 1, 2014

Traditional CAD tools generate a static solution to a design problem. Parametric systems allow th... more Traditional CAD tools generate a static solution to a design problem. Parametric systems allow the user to explore many variations on that design theme. Such systems make the computer a generative design tool and are already used extensively as a rapid prototyping technique in architecture and aeronautics. Combining a design generation tool with an analysis software and an evolutionary algorithm provides a methodology for optimising designs. This work combines NASA's parametric aircraft design tool (OpenVSP) with a fluid dynamics solver (OpenFOAM) to create and analyse aircraft. An evolutionary algorithm is then used to generate a range of aircraft that maximise lift and reduce drag while remaining within the framework of the original design. Our approach allows the designer to automatically optimise their chosen design and to generate models with improved aerodynamic efficiency. Different components on three aircraft models are varied to highlight the ease and effectiveness of the parametric model optimisation.

arXiv (Cornell University), Sep 7, 2021

This paper presents a novel total Lagrangian cell-centred finite volume formulation of geometrica... more This paper presents a novel total Lagrangian cell-centred finite volume formulation of geometrically exact beams with arbitrary initial curvature undergoing large displacements and finite rotations. The choice of rotation parametrisation, the mathematical formulation of the beam kinematics, conjugate strain measures and the linearisation of the strong form of governing equations is described. The finite volume based discretisation of the computational domain and the governing equations for each computational volume are presented. The discretised integral form of the equilibrium equations are solved using a block-coupled Newton-Raphson solution procedure. The efficacy of the proposed methodology is presented by comparing the simulated numerical results with classic benchmark test cases available in the literature. The objectivity of strain measures for the current formulation and mesh convergence studies for both initially straight and curved beam configurations are also discussed.

Thin-walled Structures, Jul 1, 2023

Computers & Structures, Oct 1, 2016

The current article presents a new implicit cell-centred Finite Volume solution methodology for l... more The current article presents a new implicit cell-centred Finite Volume solution methodology for linear elasticity and unstructured meshes. Details are given of the implicit discretisation, including use of a Finite Area method for face tangential gradients and implicit non-orthogonal correction. A number of 2-D and 3-D linear-elastic benchmark test cases are examined using hexahedral, tetrahedral and general polyhedral meshes; solution accuracy and efficiency are compared with that of a segregated procedure and a commercial Finite Element software, where the new method is shown to be faster in all cases.

International Journal for Numerical Methods in Engineering, May 12, 2022

Computers in Biology and Medicine, Sep 1, 2023

The properties of intracranial aneurysms (IAs) walls are known to be driven by the underlying hem... more The properties of intracranial aneurysms (IAs) walls are known to be driven by the underlying hemodynamics adjacent to the IA sac. Different pathways exist explaining the connections between hemodynamics and local tissue properties. The emergence of such theories is essential if one wishes to compute the mechanical response of a patient-specific IA wall and predict its rupture. Apart from the hemodynamics and tissue properties, one could assume that the mechanical response also depends on the local morphology, more specifically, the wall curvature, with larger values at highly-curved wall portions. Nonetheless, this contradicts observations of IA rupture sites more often found at the dome, where the curvature is lower. This seeming contradiction indicates a complex interaction between local hemodynamics, wall morphology, and mechanical response, which warrants further investigation. This was the main goal of this work. We accomplished this by analysing the stress and stretch fields in different regions of the wall for a sample of IAs, which have been classified based on particular local hemodynamics and local curvature. Pulsatile numerical simulations were performed using the one-way fluid-solid interaction strategy implemented in OpenFOAM (solids4foam toolbox). We found that the variable best correlated with regions of high stress and stretch was the wall curvature. Additionally, our data suggest a connection between the local curvature and local hemodynamics, indicating that the curvature is a property that could be used to assess both mechanical response and hemodynamic conditions, and, moreover, to suggest new metrics based on the curvature to predict the likelihood of rupture.

As the overlap between traditional computational mechanics and machine learning grows, there is a... more As the overlap between traditional computational mechanics and machine learning grows, there is an increasing demand for straightforward approaches to interface Python-based procedures with C++-based OpenFOAM. This article introduces one such general methodology, allowing the execution of Python code directly within an OpenFOAM solver without the need for Python code translation. The proposed approach is based on the lightweight library pybind11, where OpenFOAM data is transferred to an embedded Python interpreter for manipulation, and results are returned as needed. Following a review of related approaches, the article describes the approach, with a particular focus on data transfer between Python and OpenFOAM, executing Python scripts and functions, and practical details about the implementation in OpenFOAM. Three complementary test cases are presented to highlight the functionality and demonstrate the effect of different data transfer approaches: a Python-based velocity profile boundary condition; a Python-based solver for prototyping; and a machine learning mechanical constitutive law class for solids4foam which performs field calculations.

50th U.S. Rock Mechanics/Geomechanics Symposium, Jun 26, 2016

Engineering Fracture Mechanics, Nov 1, 2018

This study presents recent achievements in understanding the fracture behaviour of rubbermodified... more This study presents recent achievements in understanding the fracture behaviour of rubbermodified epoxy adhesives, notably the determination of the fully developed fracture process zone (FPZ) and its associated intrinsic fracture energy, G 0. The shape and size of the FPZ are identified by inspecting the fracture surfaces using SEM, and exploring subsurface damage using optical microscopy and TEM. The thickness and failure strain of the FPZ are found to be essentially the same for different fracture tests, i.e. tapered double cantilever beam and single edge notched bending tests. As a consequence, the results from different fracture tests are linked by using the geometrically transferable, true fracture properties, i.e. FPZ thickness and G 0. The variation of total fracture energy observed in different fracture tests is attributed to varying plastic deformation energy dissipated in plastic deformation zone (outside FPZ). The fracture behaviour of the adhesive is then successfully predicted by a cohesive zone model using parameters extracted from experiments.

Wind actions can have a great impact on both bridges and traffic on bridges. However, structures ... more Wind actions can have a great impact on both bridges and traffic on bridges. However, structures designed to shelter the traffic from wind can influence the aerodynamic performance of the bridge deck, especially for long-span bridges. This study compares the effect of non-perforated walls and perforated walls used as wind barriers for traffic by conducting Computational Fluid Dynamics (CFD) simulations on three-dimensional geometries of a four-lane bridge deck. Steady-state simulations employ the Reynolds-Averaged Navier Stokes (RANS) method with the k-epsilon turbulence model and all simulations use parallel computing. An open-sourced software OpenFOAM is used.

Springer eBooks, 2014

Traditional CAD tools generate a static solution to a design problem. Parametric systems allow th... more Traditional CAD tools generate a static solution to a design problem. Parametric systems allow the user to explore many variations on that design theme. Such systems make the computer a generative design tool and are already used extensively as a rapid prototyping technique in architecture and aeronautics. Combining a design generation tool with an evolutionary algorithm provides a methodology for optimising designs. This works uses NASA's parametric aircraft design tool (OpenVSP) and an evolutionary algorithm to evolve a range of aircraft that maximise lift and reduce drag while remaining within the framework of the original design. Our approach allows the designer to automatically optimise their chosen design and to generate models with improved aerodynamic efficiency.

50th U.S. Rock Mechanics/Geomechanics Symposium, Jun 26, 2016

Polymers, Dec 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Archives of Computational Methods in Engineering, Feb 2, 2021

Since early publications in the late 1980s and early 1990s, the finite volume method has been sho... more Since early publications in the late 1980s and early 1990s, the finite volume method has been shown suitable for solid mechanics analyses. At present, there are several flavours of the method, which can be classified in a variety of ways, such as grid arrangement (cell-centred vs staggered vs vertex-centred), solution algorithm (implicit vs explicit), and stabilisation strategy (Rhie-Chow vs Jameson-Schmidt-Turkel vs Godunov upwinding). This article gives an overview, historical perspective, comparison and critical analysis of the different approaches where a close comparison with the de facto standard for computational solid mechanics, the finite element method, is given. The article finishes with a look towards future research directions and steps required for finite volume solid mechanics to achieve more widespread acceptance.

Ocean Engineering, Jun 1, 2019

With global warming, the ice-covered areas in the Arctic are being transformed into open water. T... more With global warming, the ice-covered areas in the Arctic are being transformed into open water. This provides increased impetus for extensive maritime activities and attracts research interests in sea ice modelling. In the polar region, ice sheets can be several kilometres long and subjected to the effects of ocean waves. As its thickness to length ratio is very small, the wave response of such a large ice sheet, known as its hydroelastic response, is dominated by an elastic deformation rather than rigid body motions. In the past 25 years, sea ice hydroelasticity has been widely studied by theoretical models; however, recent experiments indicate that the ideal assumptions used for these theoretical models can cause considerable inaccuracies. This work proposes a numerical approach based on OpenFOAM to simulate the hydroelastic wave-ice interaction, with the Navier-Stokes equations describing the fluid domain, the St. Venant Kirchhoff solid model governing the ice deformation and a coupling scheme to achieve the fluid-structure interaction. Following validation against experiments, the proposed model has been shown capable of capturing phenomena that have not been included in current theoretical models. In particular, the developed model shows the capability to predict overwash, which is a ubiquitous polar phenomenon reported to be a key gap. The present model has the potential to be used to study wave-ice behaviours and the coupled wave-ice effect on marine structures.

This study used computational fluid dynamics (CFD) study to investigate the impact of helicopter ... more This study used computational fluid dynamics (CFD) study to investigate the impact of helicopter downwash on pedestrian comfort. The initial stage of the study involves the development of a helicopter downwash model that was compared to experimental values which showed some degree of coherence with areas situated downstream of the helicopter rotor. The initial stage was used to find suitable modelling parameters and an adequate resolution of computational mesh to produce a reliable helicopter downwash model. The final stage of the study is to integrate a helicopter in a built environment and assess the impact of downwash on pedestrian comfort. The concluding stage of the study showed that helicopter downwash effects can impose discomforting conditions in the immediate vicinity of the helicopter along with some minute propagating effects further downstream. Although its magnitude is smaller compared to effects of prevailing wind a local mitigation must be separately planned to deal with the effects of helicopter downwash.

SPE production & operations, Dec 14, 2017

Increasing the efficiency of completions in horizontal wells is an important concern in the oil a... more Increasing the efficiency of completions in horizontal wells is an important concern in the oil and gas industry. To decrease the number of fracturing stages per well, it is common practice to use multiple clusters per stage. This is done with the hope that most of the clusters in the stage will be effectively stimulated. Diagnostic evidence, however, suggests that in many cases, only one or two out of four or five clusters in a stage are effectively stimulated. In this paper, strategies to maximize the number of effectively stimulated perforation clusters are discussed. A fully 3D poroelastic model that simulates the propagation of nonplanar fractures in heterogeneous media is developed and used to model the propagation of multiple competing fractures. A parametric study is first conducted to demonstrate how important fracture-design variables, such as limited-entry perforations and cluster spacing, and formation parameters, such as permeability and lateral and vertical heterogeneity, affect the growth of competing fractures. The effect of stress shadowing caused by both mechanical and poroelastic effects is accounted for. 3D numerical simulations have been performed to show the effect of some operational and reservoir parameters on simultaneouscompetitive-fracture propagation. It was found that an increase in stage spacing decreases the stress interference between propagating fractures and increases the number of propagating fractures in a stage. It was also found that an increase in reservoir permeability can decrease the stress interference between propagating fractures because of poroelastic-stress changes. A modest (approximately 25%) variability in reservoir mechanical properties along the wellbore is shown to be enough to alter the number of fractures created in a hydraulic-fracturing stage and mask the effects of stress shadowing. Interstage fracture simulations show post-shut-in fracture extension induced by stress interference from adjacent propagating fractures. The effect of poroelasticity is highlighted for infill-well-fracture design, and preferential fracture propagation toward depleted regions is clearly observed in multiwell-pad-fracture simulations. The results in this paper attempt to provide practitioners with a better understanding of multicluster-fracturing dynamics. On the basis of these findings, recommendations are made on how best to design fracture treatments that will lead to the successful placement of fluid and proppant in a single fracture, and result in a set of fractures that are competing for growth. The ability to successfully stimulate all perforation clusters is shown to be a function of key fracture-design parameters. Prior experimental work has also clearly shown that the perforation-cluster spacing influences the fracture-growth pattern. When closely spaced multiple fractures were propagated simultaneously, some fractures were much larger than others (El-Rabaa 1982; Abass et al. 1996). It was shown that in some cases, one fracture could become the dominant fracture propagating among the clusters. Bunger et al. (2012) used an analytical model and performed a dimensional analysis to understand the most-important parameters that need to be addressed when optimizing multiple-fracture-growth problems. They considered the deflection patterns that are generated because of interaction of the fractures with existing fractures. They applied their model to a 2D fracture-growth simulator. In a later paper, the Bunger et al. (2012) model was used to understand the effect of viscosity and toughness-dominated regimes on multiple-fracture propagation (Ames and Bunger 2015). The latter used a mathematical model to couple the contributions of fluid flow, rock breakage, and perforation pressure drop to the total power requirement for the growth of multiple hydraulic fractures. Their model predicts that when the stage spacing is less than the created fracture height, the probability of multiple-fracture growth is small. The fundamental understanding their model provides can be very useful in explaining observations from numerical models. Many researchers have used the displacement-discontinuity method to model the stress interference created by hydraulic fractures. Using this method, researchers have attempted to analyze the effect of simultaneous-multiple-fracture growth (

Neurocomputing, Oct 1, 2014

Traditional CAD tools generate a static solution to a design problem. Parametric systems allow th... more Traditional CAD tools generate a static solution to a design problem. Parametric systems allow the user to explore many variations on that design theme. Such systems make the computer a generative design tool and are already used extensively as a rapid prototyping technique in architecture and aeronautics. Combining a design generation tool with an analysis software and an evolutionary algorithm provides a methodology for optimising designs. This work combines NASA's parametric aircraft design tool (OpenVSP) with a fluid dynamics solver (OpenFOAM) to create and analyse aircraft. An evolutionary algorithm is then used to generate a range of aircraft that maximise lift and reduce drag while remaining within the framework of the original design. Our approach allows the designer to automatically optimise their chosen design and to generate models with improved aerodynamic efficiency. Different components on three aircraft models are varied to highlight the ease and effectiveness of the parametric model optimisation.

arXiv (Cornell University), Sep 7, 2021

This paper presents a novel total Lagrangian cell-centred finite volume formulation of geometrica... more This paper presents a novel total Lagrangian cell-centred finite volume formulation of geometrically exact beams with arbitrary initial curvature undergoing large displacements and finite rotations. The choice of rotation parametrisation, the mathematical formulation of the beam kinematics, conjugate strain measures and the linearisation of the strong form of governing equations is described. The finite volume based discretisation of the computational domain and the governing equations for each computational volume are presented. The discretised integral form of the equilibrium equations are solved using a block-coupled Newton-Raphson solution procedure. The efficacy of the proposed methodology is presented by comparing the simulated numerical results with classic benchmark test cases available in the literature. The objectivity of strain measures for the current formulation and mesh convergence studies for both initially straight and curved beam configurations are also discussed.

Thin-walled Structures, Jul 1, 2023

Computers & Structures, Oct 1, 2016

The current article presents a new implicit cell-centred Finite Volume solution methodology for l... more The current article presents a new implicit cell-centred Finite Volume solution methodology for linear elasticity and unstructured meshes. Details are given of the implicit discretisation, including use of a Finite Area method for face tangential gradients and implicit non-orthogonal correction. A number of 2-D and 3-D linear-elastic benchmark test cases are examined using hexahedral, tetrahedral and general polyhedral meshes; solution accuracy and efficiency are compared with that of a segregated procedure and a commercial Finite Element software, where the new method is shown to be faster in all cases.

International Journal for Numerical Methods in Engineering, May 12, 2022

Current industrial practice for the fluid–structure interaction (FSI) analyses and prediction of ... more Current industrial practice for the fluid–structure interaction (FSI) analyses and prediction of aeroelastic phenomena, such as flutter, is heavily based on linear methods. These methods involve many of design limitations and envelope restrictions for aircraft. In this paper novel hybrid Reynolds-Averaged Navier–Stokes – Large Eddy Simulation (RANS–LES) turbulence model, i.e. k–Omega Shear Stress Transport Scale-Adaptive Improved Delayed Detached Eddy Simulation (k–Omega SST SA IDDES) is tested and implemented in the FSI procedure and is applied in transonic flow. This model is also compared with the lower fidelity RANS models, i.e. kOmegaSST and Spalart–Allmaras. More precisely, a strongly coupled three-dimensional (3D) FSI solver is combined with the turbulence model and large deformation updated Lagrangian finite volume structural solver in order to resolve standard computational fluid dynamics (CFD) and aeroelastic benchmark cases of transonic flow. The turbulence model combines the advanced capabilities of the existing SST, SAS and IDDES turbulence models. Unsteadiness detection deficiency of SAS is automatically supplemented by the IDDES term included in kinetic energy equation. The numerical results of Onera M6 and AGARD 445.6 validation cases are presented and compared with the existing experimental results. Discretization of the governing equations is performed by cell-centered finite volume method (FVM) on unstructured meshes. Further application of the FSI procedure for the FSI analyzes of the whole aircraft structures is one of the aims. The emphasis is made on turbulence modeling which appears to have a major impact to the prediction of FSI behavior in transonic flow domain. In this work the aeroelasticity is treated as one of the many FSI branches. Described FSI solver is custom written and implemented in OpenFOAM.