Mass transfer caused by normal localized wall injection in a laminar flow at high Schmidt number

A study is presented of mass transfer caused by normal localized fluid injection through a mean plane laminar flow, at a high Reynolds number, assuming that there is no chemical reaction in the entry zone. A solution is derived for the dynamic perturbation for the case of a porous injection region. Taking the very thin diffusion boundary into consideration, an approximate solution is derived for the injected fluid concentration distribution downstream of the injection hole near the wall. Knowledge of the local concentration makes skin friction measurement possible. An analytical expression derived for the concentration distribution downstream of the hole, clearly demonstrates that the distribution is influenced by the wall velocity gradient and by the wall friction. An instrument for measuring local wall flow has also been devised involving the placement of microelectrodes near the flow in order to detect the local concentration. The technique can be used for an instantaneous detection of pollutant species.