Synchrotron X-ray techniques for fluid dynamics

X-ray diagnostics have the potential for making quantitative measurements in many flowfields where optical diagnostics are challenging, especially multiphase flows. In the past, many such measurements have been taken with laboratory-scale X-ray sources. This review describes the measurements that are possible with synchrotron X-ray sources, which can provide high-flux, tunable, monochromatic X-ray beams that cannot be created with laboratory sources. The relevant properties of X-rays and their interactions with matter are described. The types and capabilities of various X-ray optics and sources are discussed. Finally, four major X-ray diagnostics are described in detail. X-ray radiography provides quantitative measurements of density in variable-density flows. X-ray phase-contrast imaging is used to visualize multiphase flows with high spatial and temporal resolution. X-ray fluorescence spectroscopy shows significant promise to study mixing in single-phase and multiphase flows. Small-angle X-ray scattering is a powerful technique to examine small-scale particles in flows. (orig.)