Modelling and numerical solution of variable orifice flow meter for application of respiratory

Area of Science:

• Mechanical Engineering
• Biomedical Engineering
• Fluid Dynamics

Background:

• Variable Orifice Flowmeters (VOFM) are critical components in mechanical ventilators.
• Accurate flow measurement is essential for patient respiratory support.
• Understanding fluid-structure interactions (FSI) in VOFM is key to optimizing performance.

Purpose of the Study:

• To conduct a three-dimensional computational fluid dynamics (CFD) analysis of VOFM used in mechanical ventilators.
• To investigate the influence of orifice plate geometry and thickness on flow characteristics.
• To evaluate the dynamic fluid-structure interaction (FSI) within VOFM.

Main Methods:

• Employed a dynamic fluid-structure interaction (FSI) approach using the finite volume method (FVM).
• Performed comprehensive numerical simulations utilizing a two-equation turbulence k-ω SST model.
• Validated the CFD methodology against experimental data for flexible triangular and circular orifice plates.

Main Results:

• High correlation factors were found between numerical and experimental data for membrane deflection, drag coefficient, and pressure drop.
• Orifice thickness and shape critically influence pressure drop and membrane deflection.
• Circular orifice models demonstrated more linear behavior and higher sensitivity than triangular models.

Conclusions:

• The study successfully validated CFD-FSI methodology for VOFM analysis.
• Orifice design parameters significantly affect VOFM performance in ventilators.
• Circular orifices are more sensitive and exhibit more predictable behavior for VOFM applications.