Biomedical Engineering / Fluid Mechanics Research

Transient Fluid-Structure Interaction (FSI) in Collapsible Elastic Tube

At AWJ Engineering, our team employed a segregated finite element method to analyze steady viscous fluid flow through a thin-walled elastic tube mounted between rigid sections. We coupled Navier-Stokes equations with solid mechanics equations of motion and a constitutive material model, incorporating a deforming domain (moving mesh) to capture the tube's deformation effects on fluid dynamics.

T his project highlights our expertise in multiphysics simulations for precise, real-world insights.

For more details on boundary conditions, solver settings, or similar analyses, contact us today.

Deformation of the collapsible elastic tube under fluid flow, transient FSI result

◀ Geometry of the collapsible elastic tube used in the transient FSI simulationDeformation of the collapsible elastic tube under fluid flow, transient FSI result ▶

Industry: Biomedical Engineering / Fluid Mechanics Research
Client Type: Engineering team studying fluid-structure interaction systems
Service Provided: Multiphysics simulation and fluid-structure interaction analysis
Objective: Analyze how fluid flow interacts with the deformation of a thin-walled elastic tube
Engineering Method: Transient Fluid-Structure Interaction (FSI) using COMSOL Multiphysics
Simulation Focus: Coupled analysis of viscous fluid flow and elastic structural deformation
Numerical Strategy: Segregated finite element approach with moving mesh modeling

The Client

The client was conducting research into fluid-structure interaction phenomena within collapsible elastic tubes, a topic widely studied in biomedical engineering and fluid mechanics.

Understanding the interaction between fluid flow and flexible structures is essential in applications such as:

blood flow through arteries and veins
respiratory airflow in biological airways
flexible piping systems in engineering
soft-material fluid transport systems

In these systems, the structure containing the fluid is not rigid. Instead, it deforms in response to pressure and flow forces, which in turn alters the fluid dynamics.

The client required an advanced simulation study to examine how viscous fluid flow influences the deformation of a thin elastic tube and how that deformation feeds back into the fluid behavior.

The Challenge

Fluid flow in flexible structures introduces complex feedback interactions between mechanical deformation and fluid dynamics.

Key questions the client needed to address included:

how the tube deforms under internal fluid pressure
how structural deformation alters flow velocity and pressure distribution
how steady viscous flow behaves in a flexible conduit
how to accurately simulate these interactions using computational modeling

Traditional fluid simulations assume rigid boundaries, which makes them unsuitable for systems where the flow domain itself changes due to structural deformation.

To capture realistic system behavior, the simulation required a fully coupled fluid-structure interaction approach capable of modeling both physics domains simultaneously.

Engineering Challenge

Accurately modeling collapsible tube behavior requires solving multiple sets of equations that describe both the fluid and the structure.

The simulation needed to incorporate:

Navier-Stokes equations governing viscous fluid flow
solid mechanics equations describing structural deformation
constitutive material models representing the elastic tube behavior
a dynamic mesh that updates as the structure deforms

As the tube deforms, the fluid domain changes shape. This introduces additional computational complexity because the mesh must adapt dynamically while maintaining numerical stability.

Achieving accurate results therefore required a carefully structured Multiphysics simulation framework capable of handling moving boundaries and coupled physics interactions.

Our Approach

AWJ Engineering implemented a structured simulation workflow to analyze the interaction between fluid flow and structural deformation.

System Geometry and Structural Configuration

The Simulation model consisted of a thin-walled elastic tube positioned between two rigid sections.

This configuration allowed the study to isolate deformation effects within the flexible region while maintaining stable boundary conditions at the rigid interfaces.

Multiphysics Modeling Framework

The system was modeled as a coupled fluid-structure interaction problem, allowing the simulation to capture the dynamic interaction between fluid pressure forces and structural deformation.

Two primary physics domains were integrated:

viscous fluid flow governed by the Navier-Stokes equations
elastic structural response governed by solid mechanics equations of motion

Constitutive Material Modeling

The elastic tube was assigned a constitutive material model representing its mechanical properties, ensuring that the simulation accurately captured how the structure responds to internal pressure forces.

Moving Mesh Implementation

To represent the changing geometry of the fluid domain, the simulation incorporated a deforming mesh approach.

As the elastic tube deformed under fluid pressure, the computational mesh dynamically updated to reflect the new geometry. This allowed the simulation to accurately track the feedback interaction between structural motion and fluid flow.

Segregated Finite Element Solution Strategy

To maintain numerical stability while solving the coupled equations, a segregated finite element method was implemented.

This approach solved the fluid and structural physics iteratively, ensuring stable convergence while preserving the coupling between the two systems.

The Solution

Using advanced Multiphysics modeling techniques, AWJ Engineering successfully simulated the transient behavior of fluid flow through the collapsible elastic tube.

The simulation provided detailed insights into:

deformation patterns along the flexible tube section
changes in fluid velocity caused by structural movement
pressure distribution within the deforming flow domain
the dynamic interaction between viscous forces and structural elasticity

By capturing both the structural response and the resulting changes in fluid flow, the model produced a realistic representation of fluid-structure interaction within flexible conduits.

Technologies Used

Simulation Methodology

Fluid-Structure Interaction (FSI)

Numerical Approach

Segregated finite element method

Fluid Modeling

Navier-Stokes equations for viscous flow

Structural Modeling

Solid mechanics equations of motion with elastic material model

Mesh Strategy

Deforming mesh for dynamic geometry updates

Results & Business Impact

The project delivered a reliable simulation framework capable of analyzing complex fluid-structure interaction systems.

Key outcomes included:

accurate prediction of elastic tube deformation under fluid pressure
detailed visualization of velocity and pressure changes within the flow domain
validation of a computational method for modeling flexible fluid transport systems
improved understanding of the coupling between viscous flow and structural mechanics
a robust simulation framework for future research and design studies

These insights help engineers and researchers better understand how flexible conduits behave in real-world applications.