Fulid-Structure Interaction Webinar Slides

Fluid-Structure Interaction

Kyle Mucha

Andrew Young

Marketing Manager COMSOL UK

Applications Engineer COMSOL UK

© Copyright 2016 COMSOL. COMSOL, COMSOL Multiphysics, Capture the Concept, COMSOL Desktop, COMSOL Server, and LiveLink are either registered trademarks or trademarks of COMSOL AB. All other trademarks are the property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. For a list of such trademark owners, see www.comsol.com/trademarks

Agenda • Why Simulate? – Simulating with COMSOL Multiphysics®

• Introduction to Fluid-Structure Interaction – Poll Question

• Fluid-Structure Interaction Interface – Poll Question – Moving Mesh

• Live Demo • Q&A • How To – Try COMSOL Multiphysics – Contact Us

Fluid-Structure Interaction simulation of wind acting on solar panel

Why Simulate? • Conception and understanding – Enables innovation

• Design and optimization – Achieve the highest possible performance

• Testing and verification – Virtual testing is much faster than testing physical prototypes

Fluid-Structure Interaction (FSI) in the cast and mold of an aluminum extrusion process.

Simulating with COMSOL Multiphysics® • Electrical, mechanical, fluid, and chemical simulations • Multiphysics – Include and couple all relevant physical effects • Single physics in one integrated environment • Cross-disciplinary product development

A Complete Simulation Environment COMSOL Desktop® Straightforward to use, the Desktop gives insight and full control over the modelling process

Model Builder Provides instant access to any of the model settings • CAD/Geometry • Materials • Physics • Mesh • Solvers • Results

Graphics Window Ultrafast graphic presentation, stunning visualisation

Application Design Tools Application Builder Provides all the tools needed to build and run simulation apps • Form Editor • Method Editor

Simulation Application Any COMSOL model can be turned into an app with its own interface using the tools provided in the Application Builder

Run Applications

Simulation Apps They can be run in a COMSOL® Client for Windows® and major web browsers

COMSOL Server™ It’s the engine for running COMSOL apps and the hub for controlling their deployment, distribution, and use

Product Suite – COMSOL® 5.2

Introduction to Fluid-Structure Interaction (FSI) • Examples of FSI analyses

Peristaltic pump: A roller pumps fluid along a flexible tube. Image credit: Veryst Engineering.

The air flow around a solar panel and the resultant structural stresses are computed.

Stirred mixing vessel.

Cardiovascular modelling

Introduction to Fluid-Structure Interaction (FSI) • Examples of FSI analyses

The pressure field in a lubricating layer and deformation of a tilted pad thrust bearing.

The sound pressure level radiated by a loudspeaker.

The stresses in the soil and the fluid velocity in the poroelastic domain

Solid particles in a fluid flow

Types of FSI Problems in COMSOL • Fluid flow coupled with structural deformation in solids • Acoustic-structure interaction • Porous Media and Poroelasticity • Particulate flow

Types of FSI Problems in COMSOL • Fluid flow coupled with structural deformation in solids • Acoustic-structure interaction • Porous Media and Poroelasticity • Particulate flow

Types of FSI Problems in COMSOL • Fluid flow coupled with structural deformation in solids • Acoustic-structure interaction • Porous Media and Poroelasticity • Particulate flow

Types of FSI Problems in COMSOL • Fluid flow coupled with structural deformation in solids • Acoustic-structure interaction • Porous Media and Poroelasticity • Particulate flow

Poll Question 1

Poll Question 1 • What types of FSI application are you interested in? – Fluid flow coupled with structural deformation in solids

– Acoustic-structure interaction – Porous media and poroelasticity – Particulate flow

One-Way Coupling: Small Solid Displacements • Automated solution steps: – Solve for fluid flow – Calculate total fluid stresses – Apply fluid stresses on solid boundaries

– Solve for the displacements in solids

Stresses in neonatal aortic arch as a result of pressure load calculated by fluid flow in fixed geometry

One-Way Coupling: Rigid Structures • Automated solution steps: – Calculate displacements and rotations of the rigid structure – Prescribe mesh motion according to rigid structure – Apply the velocity of the solid boundaries on the fluid walls – Solve for fluid flow

Fluid velocity in a stirred mixing vessel as a result of prescribed rigid deformations.

Two-Way Boundary Coupling • Set up FSI equations for: – Fluid flow – Structural mechanics – Moving mesh

Left: Velocity contours and Von Mises stress in vibrating beam; Right: Mesh displacement of vibrating beam.

• COMSOL automatically detects FSI boundary and sets conditions at FSI interface • Apply conditions at FSI interface: – Apply fluid boundary forces on solid boundary – Impose fluid boundary velocities based on velocity of solid boundary – Set boundary mesh displacement equal to displacement of solid boundary

Features Available for FSI Analysis • All solid and fluid capabilities in COMSOL Multiphysics are available for FSI analysis Fluid Capabilities • Laminar flow • Turbulent flow • Stokes flow • Non-Newtonian fluids • Multiphase flow • Thin fluid films

Solid Capabilities • Large deformations • Contact • Shells • Plastic materials • Hyperelastic materials • Geotechnical materials Peristaltic pump including 2way coupled FSI with contact

• FSI problems can also be coupled with any other physics field

Poll Question 2

Poll Question 2 • Which FSI coupling are you most interested in? – One way: Fluid flow → Structural deformation – One way: Structural deformation → Fluid flow – Two way: Structural deformation ↔ Fluid flow

Moving Mesh: The Challenge • COMSOL automatically sets up additional Partial Differential Equations (PDEs) for the mesh movement • Mesh follows structural deformation at FSI boundaries • Two main convergence issues: – Excessive mesh distortion – Fluid region collapsing due to contact

Mesh displacement of vibrating beam

Handling the Moving Mesh • Arbitrary Example: – Solid object (purple) moves in fluid (pink) by displacement x(t) – As solid deforms, the original mesh is distorted (in time) resulting in excessive mesh distortion and convergence difficulties

Original mesh at t = 0 s.

Solid object displacement described by x(t)

Mesh quickly becomes distorted for t > 0 s.

Helping the Mesh with Geometry Features • Additional geometric features can be added to help solve the Moving Mesh PDEs: – Helps mesh deformation maintain quality – Easiest when displacement is known • e.g. on wall boundaries where normal mesh displacement is zero but mesh nodes can still ‘slide’

Helping the Mesh with Geometry Features • Additional geometric features can be added to help solve the Moving Mesh PDEs… Even when displacement is not known! – Prescribe mesh translation based on how a point moves through FSI coupling – Use Point Integration Component Coupling to allow helper line to slide along boundary

Automatic Remeshing • COMSOL provides several criteria for initiation of remeshing • Default criterion is mesh distortion • Once threshold is me a new mesh is built on deformed geometry

Original mesh at t = 0 s.

Mesh is deformed after some time tN, where element quality is reduced

Mesh is rebuilt on geometry at t = tN

Live Demo: COMSOL Multiphysics

How this Micropump Works • When flow is against the flaps, they bend backward, narrowing the channel and increasing flow resistance • When flow is in the direction of flap tilt, the flaps bend forward, widening the channel and decreasing flow resistance • By placing titled flaps on either side of the inlet, the bending happens on opposite sides out of phase, thereby pumping net fluid to the right

Colour and arrow plot show fluid velocity

Live Demo: COMSOL Multiphysics

Why Use COMSOL Multiphysics for FSI • Easy, automated setup of fluid, structure, and moving mesh parts of FSI problems including interface conditions • Extensive capabilities in structural mechanics, fluid flow, and moving mesh • Ease of interfacing with any other physics field • Flexibility in solver selection including fully coupled direct solver for strongly coupled FSI problems • Powerful, easy-to-use design tool

Multiphysics Simulation Story: SEA FLOOR ENERGY HARVESTING

Velocity contours for a specific energy harvester configuration

NAGI ELABBASI, BRENTAN ALEXANDER, AND STUART BROWN VERYST ENGINEERING, NEEDHAM, MA, USA Extract from COMSOL News 2011 © 2016 COMSOL. All rights reserved.

uk.comsol.com/blogs

Q&A Session

Micropump with two way coupled fluid flow and structural deformation

Product Suite – COMSOL® 5.2

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