On the role of convection in free dendritic growth: Experimental measurement of the concentration field

We present an experiment designed to visualise the concentration field during the growth of dendrites. It is used to assess the role of convection by exploring three situations: growth in a gel, growth in a solution and forced imposed external flow. The observations bear on the qualitative concentration field and the quantitative measurement of the supersaturation. We show that the observations in the three cases can be correctly explained by, respectively, diffusion alone (Ivantsov theory), destabilisation of the Liquid by natural convection and a uniform flow at the scale of the dendrite.