Evolution and Structure of the Free Convective Layer Developing under a Water Surface

We experimentally studied development and statistical properties of the free convective layer under a water surface. Cooling the gas-liquid interface by water evaporation generated the convective layer. Velocity and temperature fluctuations were simultaneously measured by a laser-Doppler velocimeter and a fine thermocouple. Variances and correlations for the fluctuations were normalized by the heat flux and the thickness of the convective layer, and vertical profiles of those quantities were obtained. Their profiles were compared with those in convection over a solid wall. They had striking differences near the surface, and showed almost the same behavior in the remaining convective layer. From the profile of kurutosis, the velocity fluctuation was expected to become a Gaussin distribution in a region from near the surface to the midst of the convective layer. On the other hand, the distribution of the temperature fluctuation had two peaks near the surface, and wasn’t Gaussin in entire convective layer.