MOTION OF BUBBLES IN A VERTICAL TEMPERATURE-GRADIENT

The motions of air bubbles in a viscous silicone oil in response to buoyancy and Marangoni forces have been studied. The Marangoni forces are produced by establishing a temperature gradient in the oil which generates a surface tension gradient over the bubbles. From the thermal gradients required to balance the buoyancy and Marangoni forces, the temperature dependence of the surface tension, γ′, is found to be -0.055 mJ/m2s. This is in agreement with an independent measurement of γ′ using the pendant drop technique. © 1979.