An experimental study of pulsatile pipe flow in the transition range

Area of Science:

• Fluid dynamics
• Biofluid mechanics
• Aerodynamics

Background:

• Pulsatile flows are critical in various applications, including aerodynamics, biofluid mechanics, and gas transport.
• The transition to turbulence in pulsatile flow has significant physiological and clinical implications, potentially affecting gas transport during high-frequency ventilation and contributing to cardiovascular phenomena like valvular regurgitation and aneurysms.

Purpose of the Study:

• To investigate the characteristics of pulsatile pipe flow with a superimposed mean flow.
• To determine the conditions for flow reversal and transition to turbulence.
• To evaluate the adequacy of quasi-steady-state models for pulsatile flow.

Main Methods:

• Experimental measurements were conducted in a water flow setup.
• Data collection included mean Reynolds numbers (Re(m)) from 0 to 3000, oscillating Reynolds numbers (Re omega) from 0 to 4000, and Stokes parameter (lambda) from 7 to 15.
• Velocity profiles across different flow phases, flow reversal conditions, and pressure losses were measured.

Main Results:

• Detailed velocity profiles were obtained for various phases of the pulsatile flow.
• Conditions leading to flow reversal were identified.
• Pressure losses were quantified.
• The study assessed the applicability of quasi-steady-state models.

Conclusions:

• The transition to turbulence was determined by visual inspection of centerline velocity signals.
• Findings contribute to a better understanding of pulsatile flow dynamics and their implications in physiological and engineering contexts.
• The study provides valuable data for validating and refining flow models.