Figure 1

Schematic of the magnetic field gradients used in the primary phase encode direction for imaging. Method A shows the first few gradient values of the 2564-point spiral trajectory (inset) [14]. Method B shows the motion-sensitized version of that trajectory. The upper line is the history of rf application and data acquistion. One phase-encoded data point is acquired at each circle, at a time $t_p$ after rf pulse application. ${\overrightarrow{G}}^{\prime }$ differs from $\overrightarrow{G}$ only in a symmetrical excursion ($\overrightarrow{g}$) either side of $\overrightarrow{G}$. The superposition of $\overrightarrow{g}$ excursions upon any $\overrightarrow{k}$-space sampling scheme is possible.Reuse & Permissions

Figure 2

Bulk flow of gas is left to right in each image; the images are sensitized to the $z$ component of fluid velocity. (a) MRI map of ${\overline{U}}_3$, derived from the $g$ dependence of phase at each image voxel. Eight images acquired with different values of $g$ were zero filled and Fourier transformed to give velocity quantification in 64 bins, each of width $3\mathrm{m}/\mathrm{s}$. (b) Computational fluid dynamics (CFD) map of ${\overline{U}}_3$ for an inlet condition of uniform mean velocity $17\mathrm{m}/\mathrm{s}$ $\widehat{z}$. (c) MRI map of $D_{\mathrm{e}\mathrm{s}\mathrm{t}}$ is derived [Eq. (4)], from images of stationary and flowing gas with $g=10.2\mathrm{m}\mathrm{T}{\mathrm{m}}^{-1}$. (d) CFD map of turbulence kinetic energy ($\langle u(t{)}^2\rangle /2$), which is related to (c) through Eq. (3). In all images, velocities outside the range of the scale bar are colored like the maximum or minimum.Reuse & Permissions

Figure 3

(a) MRI map of ${\overline{U}}_3$ and (b) corresponding CFD simulation of the flow field. The obstruction is a Clark-Y wing section of mean chord length 36 mm. The Venturi flow velocity was $12\mathrm{m}{\mathrm{s}}^{-1}$ giving a Reynolds number (based upon chord length) of 150 000. These represent realistic stall conditions.Reuse & Permissions