Implementation and validation of a 1D fluid model for collapsible channels

Area of Science:

• Computational fluid dynamics
• Biomedical engineering
• Fluid-structure interaction (FSI)

Background:

• Obstructive sleep apnea (OSA) involves complex airway collapse dynamics.
• Accurate simulation of fluid-structure interaction (FSI) in collapsible geometries is challenging.
• Existing models may struggle with the highly dynamic and complex geometries found in OSA.

Purpose of the Study:

• To develop and validate a computationally efficient 1D fluid model for FSI simulations.
• To specifically address complex and completely collapsible geometries, such as those in OSA.
• To enable the use of advanced or black-box solvers for solid mechanics.

Main Methods:

• A 1D fluid model with separate fluid and solid mechanics solvers.
• Temporal discretization using a second-order scheme and spatial discretization with an asymmetrical fourth-order scheme.
• A modified area function to handle complete collapse and reopening of geometries.
• Validation against an inviscid analytical solution and a viscous flow case with complete closure.

Main Results:

• The 1D model smoothly handles completely collapsing and reopening geometries.
• Validation shows good agreement with 3D fluid simulations in static geometries when using a pressure-recovery constant.
• The model demonstrates computational speed and robustness.

Conclusions:

• The developed 1D fluid model is a fast and robust tool for FSI simulations in complex, collapsible geometries.
• It is particularly recommended for obstructive sleep apnea (OSA) research focusing on bulk flow pressure.
• The model's ability to integrate with complex solid mechanics solvers enhances its applicability.