Fluid structure interaction by means of variational multiscale reduced order models

This is the peer reviewed version of the following article: [ Tello, A, Codina, R, Baiges, J. Fluid structure interaction by means of variational multiscale reduced order models. Int J Numer Methods Eng. 2020; 121: 2601– 2625. https://doi.org/10.1002/nme.6321 ], which has been published in final form at [https://onlinelibrary.wiley.com/doi/abs/10.1002/nme.6321]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingA reduced order model designed by means of a variational multiscale stabilized formulation has been applied successfully to fluid-structure interaction problems in a strongly coupled partitioned solution scheme. Details of the formulation and the implementation both for the interaction problem and for the reduced models, for both the off-line and on-line phases, are shown. Results are obtained for cases in which both domains are reduced at the same time. Numerical results are presented for a semistationary and a fully transient case.A.T. wants to acknowledge the doctoral scholarship received from the Colombian Government-Colciencias. R.C. acknowledges the support received from the ICREA Acadèmia Research Program of the Catalan Government. J.B. acknowledges the support of the Spanish Government through the Ramón y Cajal grant RYC-2015-17367. This work is partially funded through the ELASTIC-FLOWproject, Ref. DPI2015-67857-R of the Spanish Government.Peer ReviewedPostprint (author's final draft

Monolith: a monolithic pressure-viscosity-contact solver for strong two-way rigid-rigid rigid-fluid coupling

We propose Monolith, a monolithic pressure-viscosity-contact solver for more accurately, robustly, and efficiently simulating non-trivial two-way interactions of rigid bodies with inviscid, viscous, or non-Newtonian liquids. Our solver simultaneously handles incompressibility and (optionally) implicit viscosity integration for liquids, contact resolution for rigid bodies, and mutual interactions between liquids and rigid bodies by carefully formulating these as a single unified minimization problem. This monolithic approach reduces or eliminates an array of problematic artifacts, including liquid volume loss, solid interpenetrations, simulation instabilities, artificial "melting" of viscous liquid, and incorrect slip at liquid-solid interfaces. In the absence of solid-solid friction, our minimization problem is a Quadratic Program (QP) with a symmetric positive definite (SPD) matrix and can be treated with a single Linear Complementarity Problem (LCP) solve. When friction is present, we decouple the unified minimization problem into two subproblems so that it can be effectively handled via staggered projections with alternating LCP solves. We also propose a complementary approach for non-Newtonian fluids which can be seamlessly integrated and addressed during the staggered projections. We demonstrate the critical importance of a contact-aware, unified treatment of fluid-solid coupling and the effectiveness of our proposed Monolith solver in a wide range of practical scenarios.This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (Grant RGPIN-04360-2014)