Tomography, an efficient nonintrusive technique, was employed to visualize the flow in continuous‐flow mixing and to measure the cavern volume (V c ) in batch mixing. This study has demonstrated an efficient method for flow visualization in the continuous‐flow mixing of opaque fluids using two‐dimensional (2‐D) and 3‐D tomograms. The main objective of this study was to explore the effects of four inlet‐outlet configurations, fluid rheology (0.5–1.5% xanthan gum concentration), high‐velocity jet (0.317–1.660 m s −1 ), and feed flow rate (5.3 × 10 −5 −2.36 × 10 −4 m 3 s −1 ) on the deformation of the cavern. Dynamic tests were also performed to estimate the fully mixed volume (V fully mixed ) for the RT, A310, and 3AM impellers in a continuous‐flow mixing system, and it was found that V fully mixed was greater than V c . Incorporating the findings of this study into the design criteria will minimize the extent of nonideal flows in the continuous‐flow mixing of complex fluids and eventually improve the quality of end‐products. © 2013 American Institute of Chemical Engineers AIChE J , 60: 315–331, 2014