Quantitative Mixing Measurements Using MRI of the D2O, H2O System

We have developed a quantitative technique for measuring the mean concentration distribution in turbulent, two-fluid mixing. The technique uses Magnetic Resonance Imaging (MRI) to study the mixing of de-ionized water, with its strong MRI signal, and heavy water, deuterium oxide with no signal. The MRI generates a 3D concentration distribution in liquids with good spatial resolution in about 10 seconds of scan time. Several repeated trials are used to obtain adequately converged statistics in turbulent flow. A qualification experiment in which water and heavy water mix in a 3D turbulent mixing layer has been completed. The full 3D concentration field is measured with MRI in a 256 X 24 X 9 array of voxels, giving a spatial resolution of 1.6 mm$^{3}$. Methanol is added at 33{\%} by volume to get a neutral density between the water and heavy water. Reynolds number based on the velocity difference and the downstream channel width is 3320. Planar Laser-Induced Fluorescence (PLIF) concentration measurements of water containing Rhodamine WT dye in place of the heavy water are used for validation and to obtain an uncertainty evaluation for the MR-based method.