A model for turbulent transfer processes at a solid-fluid boundary

Abstract A model is presented for the instantaneous local transport processes near the wall in turbulent pipe flows in which the momentum, concentration and thermal boundary layers are fully developed. In this model, which is an extension of the interface renewal model of Harriott[1] and makes no reference to the concept of eddy diffusivity, relatively large masses of fluid from the fully turbulent core are supposed periodically to sweep into the wall region, displacing part of the fluid there. The invading eddies, which are supposed internally laminar, then move along the wall, in whose neighbourhood they remain for finite time intervals of randomly distributed duration, exchanging mass or heat with the wall by molecular transport processes. Computational trials of the model are reported, showing it to be capable of generating fluctuations in mass-transfer rate with very similar characteristics to those obtained in experiments. Experimental mass-transfer results [2], summarised in an Appendix, are used to estimate model parameters.