1. The stability of gas envelopes trailed behind large bubbles in viscous liquids Large bubbles rising through highly viscous liquids adopt a characteristic spherical cap space (i.e. mushroom) but also develop long, thin, trailing skirts of gas. A cross-section of such a bubble is shown in the diagrams; it is held by imposing a downward velocity of UB equal to its rising velocity. Assuming that the gas within the 'skirt' is in laminar flow, that the gas pressure within the skirt rises in accordance with increases in external hydrostatic flow, that the skirt is at steady state (i.e. neither growing, nor shrinking) and that the weight of the gas can be ignored in relation to viscous forces, develop an expression to show the variables on which the thickness of the skirt, , should depend, given the conditions shown in the diagram. Assume a rectangular coordinate system, since Rc