Particle migration in nanofluids has received less than due attention in the literature, and is generally an open research topic requiring more investigation. Particle migration can have great influences on the characteristics of nanofluids through disturbing the distributions of nanoparticle concentration and thermophysical properties. This paper attempts to review and summarize the studies conducted on nanofluids, considering particle migration, including those conducted via methods such as Eulerian- Lagrangian, Buongiorno model, molecular dynamics simulation, and different theoretical approaches. Several important issues are highlighted that deserve greater attention. It is shown that there are still several hot debates for flow and thermal mechanisms in nanofluids, particularly regarding the behavior of nanoparticles. Besides, this survey identifies the challenges and opportunities for future research.
