MAGNETIC RESONANCE IMAGING OF SINGLE-AND TWO-PHASE FLOWS

摘要

Magnetic Resonance Imaging techniques are increasingly used as non-invasive tools to characterise flowing systems.During the past 10-15 years, we have seen MRI develop from a technique that can only effectively study pseudo-steady state phenomena to one which can acquire full two-and three-dimensional images in tens of milliseconds.The motivation for developing these measurement techniques is two-fold.First, we wish to image directly details of flow phenomena in optically opaque, fully three-dimensional environments that it has, as yet, not been possible to image.Second, by attaining sub-second time resolution and sub-millimetre spatial resolution, magnetic resonance provides experimental data which can be used for both the development and validation of numerical codes.In application to gas-solid fluidised beds, magnetic resonance methods have already been used to characterise, amongst other things, mixing, bubble motion and granular temperature.More recently, there has been increasing interest in undersampling techniques in data acquisition.These are not, of course, restricted to magnetic resonance experiments and are of much current interest in many areas of the physical and engineering sciences.Initial demonstration of these approaches has already been reported in gas-liquid two-phase flows.