Considerable work has already been undertaken to study the behaviour of an evaporating meniscus. Because of the complexity of the wetting process much work needs to be done to fully understand the phenomenon.
Although it has been demonstrated that the shape of such evaporating menisci depends on the intermolecular stress field and forces intervening during the process, the exact determining factors, which dictate the wetting properties, remain not fully understood and quantified. The shape of an evaporating meniscus at the exit of a capillary tube is studied by measuring the curvature and the macroscopic wetting angle. Evaporation leads to strong thermocapillary convection, which in turn is closely coupled to the wetting properties. The aim of this work is to show the effect of thermocapillary forces on the shape of an evaporating meniscus. The experimental procedure involves using pressure and temperature as constraints; the dynamic shape of the meniscus is studied. Results show a strong correlation between the contact angle and the Marangoni number. It has been observed that increasing the wall temperature would ultimately lead to a slow down of the Marangoni convection. At a given wall temperature the convection stops, this is be explained by the reduction of temperature gradient along the vapour-liquid interface. On the other hand reducing pressure has proven to lead to an increase in the apparent contact angle and an enhancement of the thermocapillary convection.