On the dispersion of a solute in a Casson fluid flow in an annulus with boundary absorption

Longitudinal dispersion of passive tracer molecules in a Casson fluid flow through an annular pipe with a reactive outer wall is studied using generalized dispersion model, which is valid for all times after the solute injection. The study describes the development of dispersive transport following the injection of a tracer in terms of the three effective transport coefficients viz. the absorption, the convection and the dispersion coefficients. The behaviour of the above three effective transport coefficients due to the variations of annular gap, yield stress and wall absorption parameter is examined. It is observed that the asymptotic convection, dispersion coefficients are dependent on yield stress of the fluid, annular gap and wall absorption parameter but the absorption coefficient is independent of the yield stress of the fluid and depends on the annular gap and wall absorption parameter. It is found that the yield stress of the fluid decreases the dispersion coefficient significantly. It is interesting to note that as annular gap decreases the dispersion coefficient also decreases. It is also seen that the dispersion coefficient is effectively decreased by interfacial mass transfer. The results of this study are of great importance in understanding the dispersion process in a catheterized artery with a reactive arterial wall.