Surfactant effects on passive scalar transport in a fully developed turbulent flow

Direct numerical simulations of fully developed turbulence in an open channel were performed. Effects of surfactants on heat transfer and the underlying turbulent structures were investigated. As surface elasticity is increased turbulent fluctuations are damped and the mean surface temperature is decreased. A surface strain model is introduced to explain this behavior in a heuristic manner. A nondimensional parameter representing the ratio of surface elastic forces to local inertial forces is introduced. It is concluded that for values of the parameter of order one, surfactants have strong effects on surface turbulence, whereas an effectively clean surface can be obtained for parameter values less than O(10?3).