On flow structures associated with large wall mass transfer coefficients in orifice flows

In this study, the turbulent flow field is simultaneously measured by stereoscopic particle image velocimetry (SPIV) and the wall mass transfer coefficient using the limiting diffusion current technique (LDCT). SPIV measurements of the flow field behind an orifice in a round pipe are performed in the cross and longitudinal sections. One-point linear and quadratic stochastic estimations are employed to calculate the conditional average of the flow field associated with the large wall mass transfer coefficient. The results suggest that the counter-rotating vortex pairs play an important role in the large wall mass transfer coefficient. The flow structures associated with a large wall mass transfer coefficient in the cross sections are found to be similar to the flow structures enhancing the wall heat transfer obtained by a theoretical analysis and numerical study in literature.