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Time Correlations in Fluid Transport Obtained by Sequential Rephasing Gradient Pulses
1Department of Chemistry, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 25, 1999
Summary
This study introduces the SERPENT (SEQuential Rephasing by Pulsed field-gradients Encoding N Time-intervals) experiment to measure fluid displacement probability. The method reveals fluid element displacement correlations over time, crucial for understanding fluid dynamics.
Area of Science:
- Fluid Dynamics
- Magnetic Resonance Imaging
- Statistical Mechanics
Background:
- Understanding fluid transport relies on characterizing displacement probability.
- Pulsed field-gradient nuclear magnetic resonance (PFG-NMR) is a powerful tool for studying molecular diffusion and flow.
Purpose of the Study:
- To present a novel PFG-NMR experiment, SERPENT, for measuring the evolution of displacement probability density in multiple time intervals.
- To demonstrate the capability of SERPENT in characterizing fluid flow and displacement correlations.
Main Methods:
- Development of the SERPENT (SEQuential Rephasing by Pulsed field-gradients Encoding N Time-intervals) pulse sequence.
- Utilizing spatial spin-labeling and multiple rephasing events with specific gradient areas (q0 + q1 + q2 = 0).
- Applying a two-dimensional Fourier transform to obtain the joint probability density W2(R1, Delta1; R2, Delta2).
Main Results:
- SERPENT successfully obtains the displacement probability density (propagator) over successive time intervals.
- The experiment allows for the direct measurement of the joint probability density for displacements in different time intervals.
- Experimental results for water flow in packed glass beads demonstrate the loss of displacement correlation as fluid elements move beyond bead diameters.
Conclusions:
- The SERPENT experiment provides a versatile method for investigating fluid displacement dynamics.
- The technique is capable of capturing short-time velocity fields and long-time displacement correlations.
- SERPENT offers insights into the history of fluctuating velocities and their impact on fluid transport.
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