Spin-echo measurements for capillary rheometry at low field

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Magnetic resonance imaging (MRI) techniques can probe fluid dynamics.
• Rheometry traditionally requires invasive measurements.
• Understanding shear-rate dependent viscosity is crucial for fluid characterization.

Purpose of the Study:

• To develop a rapid, non-invasive rheometric measurement using magnetic resonance.
• To reconstruct fluid velocity profiles and determine viscosity.
• To enhance applicability to fluids with long relaxation times.

Main Methods:

• Utilizing a single spin-echo sequence with a constant magnetic field gradient.
• Acquiring a series of spin echoes at varying echo times (TE).
• Employing a pre-measurement polarization unit for fluids with long T1 relaxation times.

Main Results:

• Phase of the spin echo is proportional to average velocity.
• Amplitude relates to velocity distribution in laminar flow.
• Reconstructed velocity profiles allow for viscosity determination.

Conclusions:

• The developed method provides a simple, non-invasive, and cost-effective rheometric measurement.
• It enables the characterization of shear-rate dependent viscosity.
• The technique is extendable to a wider range of fluids, including aqueous solutions.