• Vishal Agrawal

      Articles written in Sadhana

    • Effect of coil embolization on blood flow through a saccular cerebral aneurysm

      Vishal Agrawal Chandan Paul M K Das K Muralidhar

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      Coil embolization is a mildly invasive endovascular method for treatment of a cerebral aneurysm. The presence of a coil reduces fluid loading of the blood vessel and delays further deformation of the walls. Its effectiveness depends on the coil porosity and permeability apart from the nature of flow pulsations and its geometry. In the present work, a three dimensional numerical study of pulsatile flow of blood through an artery with saccular cerebral aneurysm is reported. The flow is unsteady but is taken to be laminar and incompressible. The coil is treated as homogeneous and isotropic porous medium. A comparative study has been carried out on aneurysms with and without a coil insert considering blood as a non-Newtonian fluid. The simulation is carried out for Reynolds numbers $Re$ = 500 and 1500. Results show that the velocity magnitude within the coil embolized aneurysm becomes negligible after coil insertion. The wall shear stress within the aneurysm decreases to a great extent for both Reynolds numbers. Pressure levels remain relatively unchanged. Overall, reduced wall loading with a coil stabilizes the growth of the aneurysm and thus provides an advantage.

    • NURBS-based isogeometric analysis for stable and accurate peeling computations

      VISHAL AGRAWAL SACHIN S GAUTAM

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      Numerical solution of adhesive peeling problems presents significant computational challenges. This is due to the large peeling stresses that occur in the very narrow zone ahead of the peeling front. The available literature offers solutions using either higher-order Lagrange-enriched finite-element (FE) or nonuniform rational B-spline (NURBS)-enriched FE strategies. However, no work that fully utilizes the intrinsic advantageous features of isogeometric analysis and systemically explores the influence of NURBS discretizations exists on the adhesive peeling computations. Thus, the objective of the present work is to fill this research gap by carrying out a comprehensive and detailed isogeometric analysis of peeling problems and also to study the effect of different classes of NURBS discretizations on the stability and accuracy of peeling contact computations. In particular, higher-continuous and higher-order NURBS discretizations that are constructed with different combinations of various isogeometric refinement strategies are employed. In addition to this, higher-order Lagrange discretizations are adopted to perform comparative assessment of various isogeometric NURBS discretizations. The comparison is carried out in terms of accuracy, stability and computation cost for peeling analysis. The obtained results demonstrate the advantages of the NURBS discretizations: higher-continuous NURBS discretization delivers an accuracy similar to that with the higher-order Lagrange discretization at a much lower computational cost. Further, the higher-order NURBS discretizations significantly improve the stability and accuracy again at a lower computational cost as compared with higher-order Lagrange discretizations

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