New invasive image velocimetry applicable to dense multiphase flows and its application in solid–liquid suspensions

An invasive image velocimetry (IIV) is developed for measurement of multiphase flows, which starts from the photographs taken by a vision probe and then determines the flow fields after a series of images processing steps. It overcomes the limitations of laser‐based velocimetries, especially inapplicability to dense multiphase flows. The measurement results using IIV in the single phase stirred tank agree well with those by laser Doppler velocimetry except for the region close to impeller. The disagreement could mainly be attributed to long frame intervals so that the one‐quarter rule of correlation evaluation cannot be satisfied. As it is applied in solid–liquid systems with particles loads above the upper limit of laser‐based techniques without refractive matching, the direct and indirect interactions between particles and liquid are preliminarily analyzed based on instantaneous solid–liquid flows. More accurate mean velocities are obtained which provides a useful benchmark for computational fluid dynamics modeling validation in dense multiphase flow.