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Agrawal, Vishal
Publications (2 of 2) Show all publications
Agrawal, V., Kulachenko, A., Scapin, N., Tammisola, O. & Brandt, L. (2024). An efficient isogeometric/finite-difference immersed boundary method for the fluid–structure interactions of slender flexible structures. Computer Methods in Applied Mechanics and Engineering, 418, Article ID 116495.
Open this publication in new window or tab >>An efficient isogeometric/finite-difference immersed boundary method for the fluid–structure interactions of slender flexible structures
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2024 (English)In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 418, article id 116495Article in journal (Refereed) Published
Abstract [en]

In this contribution, we present a robust and efficient computational framework capable of accurately capturing the dynamic motion and large deformation/deflection responses of highly-flexible rods interacting with an incompressible viscous flow. Within the partitioned approach, we adopt separate field solvers to compute the dynamics of the immersed structures and the evolution of the flow field over time, considering finite Reynolds numbers. We employ a geometrically exact, nonlinear Cosserat rod formulation in the context of the isogeometric analysis (IGA) technique to model the elastic responses of each rod in three dimensions (3D). The Navier–Stokes equations are resolved using a pressure projection method on a standard staggered Cartesian grid. The direct-forcing immersed boundary method is utilized for coupling the IGA-based structural solver with the finite-difference fluid solver. In order to fully exploit the accuracy of the IGA technique for FSI simulations, the proposed framework introduces a new procedure that decouples the resolution of the structural domain from the fluid grid. Uniformly distributed Lagrangian markers with density relative to the Eulerian grid are generated to communicate between Lagrangian and Eulerian grids consistently with IGA. We successfully validate the proposed computational framework against two- and three-dimensional FSI benchmarks involving flexible filaments undergoing large deflections/motions in an incompressible flow. We show that six times coarser structural mesh than the flow Eulerian grid delivers accurate results for classic benchmarks, leading to a major gain in computational efficiency. The simultaneous spatial and temporal convergence studies demonstrate the consistent performance of the proposed framework, showing that it conserves the order of the convergence, which is the same as that of the fluid solver.

Place, publisher, year, edition, pages
Elsevier BV, 2024
Fluid–structure interactions, Geometrically exact beam model, Immersed-boundary method, Incompressible flows, Isogeometric analysis, Partitioned solvers
National Category
Computational Mathematics Applied Mechanics Fluid Mechanics and Acoustics
urn:nbn:se:kth:diva-338863 (URN)10.1016/j.cma.2023.116495 (DOI)001096820100001 ()2-s2.0-85174171313 (Scopus ID)

QC 20231031

Available from: 2023-10-31 Created: 2023-10-31 Last updated: 2023-11-30Bibliographically approved
Das, S. K., Agrawal, V. & Gautam, S. S. (2024). Assessment of various isogeometric contact surface refinement strategies. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 46(4), Article ID 175.
Open this publication in new window or tab >>Assessment of various isogeometric contact surface refinement strategies
2024 (English)In: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 46, no 4, article id 175Article in journal (Refereed) Published
Abstract [en]

Since its inception, isogeometric analysis (IGA) has shown significant advantages over Lagrange polynomials-based finite element analysis (FEA), especially for contact problems. IGA often uses C1-continuous non-uniform rational B-splines (NURBS) as basis functions, providing a smooth description of kinematic variables across the contact interface. This leads to increased accuracy and stability in the numerical solutions. However, from the existing literature on isogeometric contact analysis, it is not yet clear what interpolation order and continuity of NURBS one should employ to accurately capture the distribution of contact forces across the contact interface. The present work aims to fill this gap and provides a comparative assessment of different NURBS-based standard (conventional) refinement strategies for contact problems within the IGA framework. A recently proposed refinement strategy, known as the varying-order (VO) based NURBS discretization, has demonstrated its capability to refine geometry through the implementation of order elevation in a controlled manner. However, a detailed investigation that directly compares the VO based NURBS discretization with the standard NURBS discretization has not yet been carried out. Therefore, a thorough study of the VO based discretization strategy is also conducted, evaluating its effectiveness in comparison with the standard discretization strategy for contact problems. For this, a few examples on contact problems are solved using an in-house MATLAB® code. The solution to these examples shows that quadratic order standard NURBS discretization is sufficient to achieve the desired level of solution accuracy just by increasing the mesh size. It is further demonstrated that VO based discretization can achieve much higher accuracy than standard discretization, even with a coarse mesh, by generating additional degrees of freedom in the contact boundary layer. In addition, VO based discretization makes considerable savings in analysis time to achieve the same accuracy level as standard discretization.

Place, publisher, year, edition, pages
Springer Nature, 2024
Contact mechanics, Isogeometric analysis, NURBS discretization, Refinement strategies, Varying-order NURBS
National Category
Computational Mathematics
urn:nbn:se:kth:diva-344323 (URN)10.1007/s40430-024-04712-5 (DOI)001173764700002 ()2-s2.0-85186769839 (Scopus ID)

QC 20240318

Available from: 2024-03-13 Created: 2024-03-13 Last updated: 2024-03-18Bibliographically approved

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