Study of turbulent flow using Half-Fourier Echo-Planar imaging

Abstract

The Echo-Planar Imaging technique combined with a partial Fourier acquisition method was used to obtain velocity images for liquid flows in a circular cross-section pipe at Reynolds number of up to 8000. This partial-Fourier imaging scheme is able to generate shorter echo times than the full-Fourier Echo-Planar Imaging methods, reducing the signal attenuation due to T2* and flow. Velocity images along the z axis were acquired with a time-scale of 80 ms thus obtaining a real-time description of flow in both the laminar and turbulent regimes. Velocity values and velocity fluctuations were computed with the flow image data. A comparison plot of NMR velocity and bulk velocity and a plot of velocity fluctuations were calculated to investigate the feasibility of this imaging technique. Flow encoded Echo-Planar Imaging together with a reduced data acquisition method can provide us with a real-time technique to capture instantaneous images of the flow field for both laminar and turbulent regimes.

MRI: a tool for measuring turbulent intensities in flow systems

“…This occurs because of the additional phase variation that is generated by the presence of turbulent fluctuation of the velocities resulting in a loss of coherence and subsequently signals attenuation. To address this challenge, methods have been developed [9,10] which are capable of resolving the velocity of fast moving fluid with Reynolds number up to 10000. A Reynolds number is a dimensionless quantity which indicates whether the flow of fluid is steady (laminar) or steady on average but with small unsteady changes (turbulent).…”