DETACHMENT OF DROPS AND BUBBLES IN FLOW-FIELDS

The detachment of drops and bubbles in a flow field is of interest in such diverse situations as the spraying of pesticides, meltdown in nuclear reactors, and liquid-liquid extraction. The drop shape and its maximum volume are affected by the drag force acting on the drop due to the flow field. Including this drag force in the gravitational force as a body force has the advantage of not altering the shape of the drop but only its size. The gravitational acceleration g' corresponding to a dimensionless force F = fc1/2/sigma is related to the maximum drop volume V(max) = upsilon(max)'(c')3/2 , and the ambient gravitational acceleration g by g'/g = 1 + F/V(max)(g'/g)3/2 in which the volume V(max) is only a function of the contact angle between the drop, the ambient fluid and the solid surface to which it is attached; the capillary constants are defined by c = DELTArhog/sigma and c' = DELTArhog'/sigma. The drop volume detaching from the solid surface is less than the maximum volume but is greater than that detaching from a nozzle because the contact radius of the drop remaining on the surface is smaller than that of the original drop.