Measurement of the turbulent mass flux with PTV in a street canyon

Simultaneous measurement of velocity and concentration provides a tool for studying the turbulent diffusion. This quantity until now was mainly modeled and not measured and it plays an essential role in turbulent diffusion of pollutant. sent a new technique to measure the turbulent mass flux vector, u′c′, based on the same PIV/PTV images, employed for both instantaneous velocity and concentration measurements. Then we applied the new technique to check the correctness of the model widely used for the turbulent mass flux in RANS simulations, in a street canyon type flow. We found places where the turbulent diffusion is opposite to the gradient in mean concentration.