Documents published in Scipedia

• A certified wavelet-based physics-informed neural network for the solution of parameterized partial differential equations

  L. Ernst, K. Urban

  coupled2023.

  
  

  Abstract

  Physics Informed Neural Networks (PINNs) have frequently been used for the numerical approximation of Partial Differential Equations (PDEs). The goal of this paper is to construct PINNs along with a computable upper bound of the error, which is particularly relevant for model reduction of Parameterized PDEs (PPDEs). To this end, we suggest to use a weighted sum of expansion coefficients of the residual in terms of an adaptive wavelet expansion both for the loss function and an error bound. This approach is shown here for elliptic PPDEs using both the standard variational and an optimally stable ultra-weak formulation. Numerical examples show a very good quantitative effectivity of the wavelet-based error bound.

  Abstract
  Physics Informed Neural Networks (PINNs) have frequently been used for the numerical approximation of Partial Differential Equations (PDEs). The goal of this paper is to construct [...]

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• Multiphysical Modeling of Soft Tissue-Stent Interaction

  S. Reese, K. Manjunatha, J. Shi, M. Sesa

  coupled2023.

  
  

  Abstract

  The prevalence of in-stent restenosis after percutaneous coronary intervention necessitates the development of computational tools to derive pathophysiological inferences and finetune interventional procedures patient-specifically. In this context, a multiphysics framework is presented herein that captures the chemo-mechano-biological interaction involved. Strategies that could potentially accelerate the computations as well as add versatility to them are shortly discussed. We hence take a minute step towards enabling computer-assisted clinical practices.

  Abstract
  The prevalence of in-stent restenosis after percutaneous coronary intervention necessitates the development of computational tools to derive pathophysiological inferences [...]

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• On the 2D-1D Coupling in Numerical Simulations of Simplified Air Flow Model in Human Airways

  coupled2023.

  
  

  Abstract

  This paper presents selected results regarding the implementation, validation and testing of a simple 2D-1D coupled model designed to capture some essential features of the oscillatory air flow in human respiratory system. The model relies on a 2D flow model solved by a simple finite-difference scheme in the immersed boundary setting. The incompressible fluid flow from this model is coupled to a simplified 1D fluid-structure-interaction model simulating the flow in a tube with elastic walls. Some first results obtained using the coupled 2D-1D model in an oscillating (Womersley-like) type of flow are presented and discussed in detail. The influence of model parameters is explored for a range of physically relevant settings.

  Abstract
  This paper presents selected results regarding the implementation, validation and testing of a simple 2D-1D coupled model designed to capture some essential features of the [...]

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• Assessing Scaling and Kinematic Errors in a Coupled Experimental-Computational Infant Musculoskeletal Model

  T. Chambers, C. Walck, V. Huayamave, E. Mannen

  coupled2023.

  
  

  Abstract

  Musculoskeletal models are valuable tools that enable the study and quantification of biomechanical parameters, allowing researchers to better understand the mechanisms influencing or contributing to human movement. Furthermore, musculoskeletal models have the potential to serve as diagnostic tools for identifying pathologies and disorders, such as developmental dysplasia of the hip. However, current musculoskeletal models are developed using adult subjects, with only a few studies focusing on infant populations, despite the greatest growth rate being in early infancy. Therefore, the objective of this study was to evaluate the impact of multiple linear scaling approaches of increasing complexity on the development of an infant musculoskeletal model. Motion capture technology was used to collect data from the spontaneous kicking movement of a 2.4-month-old infant lying supine. The experimental motion capture data and anthropometric measurements were used to scale the generic gait2392 OpenSim model. Four linear scaling methods of increasing complexity were used: uniform (Uni), nonuniform (Non), nonuniform with knee and ankle joint centers (NAKJCs), and nonuniform with knee, ankle, and regression-derived hip joint centers (NHJCs). Results suggest that the maximum marker errors decreased with the increasing complexity of the scaling approach. The Uni scaling approach resulted in the largest scaling and kinematic errors, with maximum marker errors of 4.92 cm and 5.30 cm, respectively. The NHJCs scaling approach had the lowest maximum marker errors, with errors of 4.17 cm and 4.36 cm, respectively. The scaling method used to develop infant musculoskeletal models should be considered carefully, especially when using linearly scaling generic models developed using adult cadaveric data.

  Abstract
  Musculoskeletal models are valuable tools that enable the study and quantification of biomechanical parameters, allowing researchers to better understand the mechanisms influencing [...]

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• A Novel Musculoskeletal-driven Exoskeleton Framework for Spina Bifida Rehabilitation in Infants

  V. Huayamave, T. Chambers, E. Vela, W. Kim, E. Centero, B. Macumber

  coupled2023.

  
  

  Abstract

  Soft exoskeletons are lightweight robotic devices currently used for physical therapy and rehabilitation. Most of the current research on soft exoskeletons has focused on the adult population, providing limited options for infant physical therapy and rehabilitation. Spina bifida, a condition affecting the infant’s brain and spinal cord, requires muscle movement treatment through physical therapy. Coupling physiological infant movement with soft robotics can provide solutions for rehabilitation and physical therapy. This study couples joint kinematics from a novel musculoskeletal model with a soft-robotic exoskeleton that uses vacuum-powered artificial muscles. The accuracy of the exoskeleton is assessed when replicating physiological infant kicks. Knee joint kinematics from the musculoskeletal model during infant movement were used to drive the soft exoskeleton. Preliminary results showed that the robotic system replicated infant kicks with lower frequency and small ranges of motion (RMS < 2 degrees) more accurately than those with higher frequency and large ranges of motion (RMS > 6 degrees). The proposed framework has the potential to replicate physiological infant kicks that could be used for infant physical therapy and rehabilitation.

  Abstract
  Soft exoskeletons are lightweight robotic devices currently used for physical therapy and rehabilitation. Most of the current research on soft exoskeletons has focused on [...]

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• A mechanobiological bone remodelling model coupling bone physiology and systemic calcium and phosphorus homeostasis

  J. Martínez-Reina, J. Calvo-Gallego, F. Gutiérrez-Milán, P. Pivonka

  coupled2023.

  
  

  Abstract

  In this work we couple a physiologically based mathematical model of integrated calcium and phosphorus homeostasis to a cell population bone remodelling model and to a pharmacokinetics (PK) - pharmacodynamics (PD) model of denosumab (Dmab), an antiresorptive drug administered to combat osteoporosis (OP). The model of Ca and P homeostasis allows to incorporate the effect of factors such as Ca dietary changes, vitamin D supplementation, concurrence of renal deficiency or hyperparathyroidism into the study of OP and its treatment.

  Abstract
  In this work we couple a physiologically based mathematical model of integrated calcium and phosphorus homeostasis to a cell population bone remodelling model and to a pharmacokinetics [...]

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• An HPC Multi-Physics Framework for Next-Generation Industrial Aircraft Simulations

  E. Fadiga, F. Rondina, T. Benacchio, D. Malacrida, L. Capone, S. Oliani

  coupled2023.

  
  

  Abstract

  The aerodynamic performance of industrial aircraft is strongly coupled with the structural deformation under aerodynamic load. Consequently, multi-physics simulations represent an important asset during the design and optimization phases. Most of the Fluid-Structure Interaction (FSI) coupling approaches adopted by researchers and engineers can be divided into monolithic and partitioned techniques. The monolithic coupling, which consists of a unique system of equations for the coupled problem, is usually characterized by higher robustness and easier scalability. However, this approach is inherently customized for specific applications and requires a significant development effort. The partitioned coupling links existing software on a higher level, benefitting from higher flexibility and lower time-to-solution. As the computational world marches towards the exascale, black-box coupling libraries such as preCICE [2] aim to combine the flexibility and user-friendliness of partitioned approaches with complete and efficient usage of the available computational power. This paper focuses on aeroelasticity analyses currently performed at the Leonardo Labs facilities, exploiting the recently installed davinci-1 supercomputer [14]. Open-source CFD and structural dynamics software applications are coupled using preCICE to conduct fully threedimensional FSI analyses of aeroelastic test cases of industrial interest. The activities are part of a broader Digital Innovation industrial strategy centred on Digital Twins combining high-fidelity, highly scalable numerical simulations with data-driven AI models.

  Abstract
  The aerodynamic performance of industrial aircraft is strongly coupled with the structural deformation under aerodynamic load. Consequently, multi-physics simulations represent [...]

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• Hemodynamic evaluation of aortic aneurysms using FSI simulations

  B. Chitneedi, C. Karliampas

  coupled2023.

  
  

  Abstract

  The work focuses on understanding aortic blood flow dynamics and emphasize the importance of considering the flexible aortic wall model in assessing cardiovascular health and identifying potential risk factors for aneurysm and related conditions. In this paper, a fluidstructure interaction (FSI) study of vascular blood flow based on the partitioned approach using open-source software tools, OpenFOAM for Computational Fluid Dynamics (CFD) and CalculiX for Computational Structural Mechanics (CSM), coupled through the preCICE tool is presented. The FSI simulations were performed on raw and simplified (based on area of interest) patient-specific models of aneurysmatic blood vessels, considering Newtonian fluid and laminar flow assumptions. The arterial wall was modeled using the CalculiX’s isotropic linear elastic model and the communication of data is handled by preCICE. The biomedical metrics such as the Time-Averaged Wall Shear Stress (TAWSS) and the Oscillatory Shear Index (OSI) in correlation with cardiac cycles were quantified to predict rupture prone regions.

  Abstract
  The work focuses on understanding aortic blood flow dynamics and emphasize the importance of considering the flexible aortic wall model in assessing cardiovascular health [...]

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• Data-Parallel Radial-Basis Function Interpolation in preCICE

  D. Schneider, T. Schrader, B. Uekermann

  coupled2023.

  
  

  Abstract

  We present data-parallel approaches to solve radial-basis function interpolation problems in the context of partitioned multi-physics simulations, where interpolation methods are required to transfer coupling data between non-matching vertex clouds. Data-parallel approaches are a key component for the efficient use of accelerator cards and thus for performance portability on modern compute platforms. The presented approach is integrated into the open-source coupling library preCICE. After discussing different implementation strategies, we introduce a solution based on thelinear algebra library Ginkgo, which provides a common abstraction layer for cross-platform performance with focus on solving sparse linear systems. The new implementation exploits accelerator cards for both, matrix assembly as well as solving the resulting linear system. The capability of the presented approach is compared to already existing implementations in preCICE using a turbine blade geometry

  Abstract
  We present data-parallel approaches to solve radial-basis function interpolation problems in the context of partitioned multi-physics simulations, where interpolation methods [...]

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• Implementation and Formulation of a Multi-Region, Electromagnetic Solver for Discontinuous Media

  A. Bogaers, W. Roos, Q. Reynolds, J. Zietsman

  coupled2023.

  
  

  Abstract

  The formulation and implementation of a finite-volume, multi-region, electromagnetic solver into OpenFOAM, and coupled using preCICE is presented, to enable the solution of electromagnetic problems with large material discontinuities.

  Abstract
  The formulation and implementation of a finite-volume, multi-region, electromagnetic solver into OpenFOAM, and coupled using preCICE is presented, to enable the solution [...]

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