Life Sciences Applications: Modeling and Simulation for Biomedical Device Design

Kristian.Debus@cd-adapco.com

SGC 2013

• Biomedical device design and the regulatory agencies

• Modeling capabilities for the design of various devices • Respiratory • Medical equipment • Cardiovascular

• Fluid Structure Interaction (FSI): implicit coupling of STAR-CCM+

and Abaqus

Modeling and Simulation for Biomedical Device Design

Medical Device Application Range

Macro Devices – Stents – Pumps – Heartvalves – Artificial Organs – Catheters – Pacemakers – Respiratory Aids

Micro Devices – Lab on a Chip – Implanted sensors – Implanted drug delivery

Diagnostics – MRI/CT Scanners – Ultrasound

Life Support – Lung/Heart Machine – Dialysis

Monitors – Blood Pressure – ECG, EEG, dissolved gases

Therapeutic – Lasers – Infusion Pumps

forming a V&V committee that is application-specific to the medical device industry

Some Example Cases: – FDA CPI I – Nozzle – Hemolysis Modeling – Drug delivery to the eye, by intravitreal injection – Oscillatory Pipe Flow – Flow in a Flexible Pipe – CFD Challenge – Aneurysms – Porous media modeling (Fiber bundles) – Oxygenator – Particle tracking etc. etc…..

ASME V&V 40 Committee

Inhaler Modeling at ARUP

STAR-CCM+ at VIASYS (Carefusion) Healthcare

Mouth Cavity – Inhalation Model

Mouth Cavity

Simpleware lung demo case

Simpleware was used to obtain the complex geometry from MRI of the human body

Microfluidics

8

Formation of droplet in flow-focusing geometry

Heat Transfer, Electronics Cooling & Noise Modelling

Ventilation flow and convective cooling as required for MRI/CT scanners, ICU devices

• Surface wrapping utilized to automatically prepare surface • Volumetric heat sources • Multiple fan models with fan curves

Workflow: Meshing of Patient Specific Data

Surface Wrapping, STL Cleanup & Polyhedral Meshing Rapid Turnaround of Complex Geometry

Dissected Aorta Polyhedral Mesh, Geometry Provided by the Methodist DeBakey Heart and Vascular Center, Houston (Dr. Christof Karmonik, Dr. Mark

Davies, Dr. Alan Lumsden, Dr. Jean Bismuth)

AAA (Abdominal Aortic Aneurysm) Geometry Provided by Computational Clinical

Modeling, New Jersey (Chris Ebeling)

Cardiovascular flow wave form from applied at the inlet

Material properties of blood (Newtonian Approximation) » Density = 1056 kg m-3 » Dynamic Viscosity = 0.0035 Pas

Windkessel parameters to define the outlet condition: » Z = 1.1x107 [kg m-4 s-1] » R = 1.45x108 [kg m-4 s-1] » C = 1.45x10-8 [m4 s2 kg-1]

Laminar flow model • Implicit Unsteady model (dt = 0.001 s) • Coupled implicit solver

Simulation was run for a number of cycles to ensure a period response was achieved.

Model setup

Z2

R2

C2

Z3

R3 C

3

Z1

R1

C1

Z4

R4

C4

Analytical solution [2] • Maximum outlet pressure = 93mmHg.

Numerical solution • Maximum outlet pressure = 92.2 mmHg

Preliminary Results

Analytical Solution

[2] Brown A. G., Patient-Specific Local and Systemic Haemodynamics in the Presence of a Left Ventricular Assist Device, 2012. PhD Thesis, The University of Sheffield.

Fluid Structure Interaction

• Driven by highly compliant vessels and membranes, structurally impacted by mechanical devices.

• STAR-CCM+ couples directly to Abaqus (Simulia) through a co-simulation API fully coupled, implicit, two-way FSI

Examples include: Blood Pumps (LVADs), Vena Cava Filter, Stents, Graft Bypass, Diagnostics for Arterial Flows or Lung Models etc. etc.

Counter Intuitive: Pulse through an Extremely Flexible Tube

• Pressure pulse in fluid travels only at a speed of near 50 m/s when bulk modulus of the solid is 0.1GPa.

• For completely rigid pipe: pulse would

travel at sound speed of the fluid (1500 m/s).

• Kinetic energy is primarily being converted into radial strain energy in the solid when it travels there is nothing left to push the pulse down the pipe.

• The step size is chosen so that for the expect wave speed, the wave travels one cell down the axis. So the smaller the modulus, the smaller the wave speed, the larger the time step yet still accurate and stable!!

Damon Afkari, Universidad Politécnica de Madrid

FSI Simulation of Pulsatile Blood Flow in Aortic Arch: Coupling Abaqus and STAR-CCM+

Universidad Politécnica de Madrid, Damon Afkari: PhD Student Developed Proprietary Explicit Coupling Methodology • Now Implicit Coupling with

Abaqus • Focus on Fast Turn Around to Aid

Surgeon Decision Making

Aortic Dissection

CAD

FSI for Heart Valve Biomechanics (University of Connecticut, Prof. Wei Sun, Dr. Eric Sirois)

CFD Meshing & Morphing • Polyhedral mesh

– 0.43 mm base size

• Leaflet motion -> Star-CCM+ morphing

– Separate motion for each leaflet – Interpolated and mapped

• Arbitrary Lagrangian-Eulerian (ALE) mesh morphing

• Automated re-meshing for low quality or zero-volume cells

– “Minimum points in a gap” of 4 nodes used to control proximity

– Mesh varied from ~700k to 1.8M

Valve Leaflet

Cross-section of CFD model showing polyhedral

mesh.

FEA 1st Run

Experiment

CFD 1st Run

Leaflet Motion

FEA 2nd Run

CFD 2nd Run

Leaflet Motion

Leaflet Motion Comparison

Hemodynamics Comparison

Far-Field Pressure

CFD Velocity Magnitude and WSS Side view Top view

Bottom view

WSS

Heart Valve FSI: Edwards LifeSciences

Biomedical FSI Applications • Stent Implants: AAA, Coronary,

Carotid Arteries etc. • Vena Cava Filters • Heart Valves • Graft Bypass • Aneurysm Diagnostics Models • Respiratory/Lung Models

FSI & Overset Meshes