Flush-mounted hot film anemometer accuracy in pulsatile flow.

Area of Science:

• Fluid dynamics
• Biomedical engineering
• Hemodynamics

Background:

• Accurate measurement of wall shear stress (WSS) is crucial for understanding physiological flows.
• Pulsatile flows, characteristic of cardiovascular systems, present unique challenges for WSS measurement.
• Hot film anemometry is a potential technique for WSS assessment.

Purpose of the Study:

• To evaluate the accuracy of flush-mounted hot film anemometer (HFA) probes for measuring WSS in pulsatile flows.
• To compare measured WSS waveforms with theoretical predictions in a rigid tube model.

Main Methods:

• Experiments were conducted using fully developed pulsatile flow in a rigid straight tube.
• HFA probe measurements were calibrated using steady flow conditions.
• Measured WSS waveforms were compared against theoretical WSS waveforms derived from flow rate measurements and established fluid dynamics principles.

Main Results:

• Measured and theoretical WSS waveforms showed close agreement during the systolic phase, with an average deviation of 14% at peak systole.
• Agreement between measured and theoretical WSS was poor during the diastolic phase.
• The discrepancy during diastole was attributed to flow reversal and the diminished frequency response of the HFA probe at low shear rates.

Conclusions:

• Flush-mounted HFA probes can provide accurate WSS measurements in pulsatile flows, particularly during systole.
• The probe's performance is limited during diastole due to flow reversal and frequency response limitations.
• Further development may be needed to improve HFA probe accuracy in complex diastolic flow conditions.