Flush-mounted anemometer probes have been used to further study characteristics of the viscous sublayer for both Newtonian and drag reducing solutions, with particular emphasis given to low Reynolds number turbulent tube flow. Experimental measurements for the mean frequency of bursting or renewal within the wall region are compared with theoretical predictions obtained on the basis of the surface renewal and penetration model.
Both theory and experiment taken together suggest that the effect of the mean axial pressure gradient on the viscous sublayer becomes important for the deeper molecular penetration associated with low Reynolds number flow. Also, a pronounced lessening of the frequency of bursting within the wall region has been predicted and measured for the addition of a drag reducing agent
