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Abstract Helical blood flow, characterized by its spiral motion, is a crucial physiological phenomenon observed in various circulatory structures, including the heart, aorta, vessel bifurcations, umbilical cord, and respiratory system. Despite its importance, a comprehensive understanding of helical flow dynamics is limited. This study aims to investigate the transition from laminar to turbulent flow in helical tubes under both steady and pulsatile conditions. An experimental setup was developed, featuring a closed-loop system with a pulsatile flow generator and steady pump, producing sinusoidal waveforms with adjustable frequencies and amplitudes. Five helical tube models, varying in curvature radius and torsion, were fabricated with a fixed inner diameter of 15 mm. High-frequency pressure transducers, ultrasonic flow sensors, and Laser Doppler Velocimetry (LDV) were employed to visualize flow fields and measure turbulence kinetic energy (TKE). Results indicate that helical tube geometry significantly impacts turbulence transitions. Specifically, larger curvature radii stabilize the flow and reduce turbulence downstream, while smaller radii lead to earlier transitions to turbulence. Under steady flow conditions, the critical Reynolds number (Re) for turbulence onset was found to be around 2300 upstream, similar to straight pipes, but significantly higher turbulence levels were observed downstream. Pulsatile flow with high pulsatility indices (PI > 3) near transitional Re markedly increases turbulence, particularly downstream, with large bursts of turbulence occurring during the deceleration phase. These findings enhance the understanding of helical flow dynamics and have implications for biomedical device design, diagnostics, and treatments for circulatory disorders.
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Bidirectional Venturi Flowmeter Based on Capacitive Sensors for Spirometry
Abstract In this work, a portable venturi tube capable of measuring bidirectional respiratory flow is developed and correlated the measurements to pulmonary function. Pressure signals are transduced using flexible and compressible capacitive foam sensors embedded into the wall of the device. In this configuration, the sensors are able to provide differential pressure readings, from which the airflow rate passing through the tube could be extrapolated. Utilizing the venturi effect, the geometry of the spirometer tube is designed through finite element analysis to measure respiratory airflow during inhalation and exhalation. The device tube is 3D‐printed and used to measure tidal breathing and deep breathing, along with peak expiratory flow rates, on a healthy individual. This spirometer design allows for easy‐to‐use point‐of‐care diagnoses and has the potential to improve the care of respiratory illnesses.
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- PAR ID:
- 10441336
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 8
- Issue:
- 18
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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