COMPUTATION OF INTERFACE SHAPE AND MAXIMUM FORCE IN SURFACE-TENSION MEASUREMENTS

A novel and efficient iterative optimization method has been developed for computing the maximum force observed as a cylinder is withdrawn f rom an annular interface between two fluids. This method can be used t o find the interfacial tension from the experimental value of the maxi mum force and several other parameters related to the experiment. It a lso produces the interface shape, which can be highly curved when the vessel diameter is large relative to the cylinder diameter. The method , based on successive quadratic programming and the use of Lagrange mu ltipliers to handle equality constraints, is not specific to the surfa ce tension problem, but can be applied in the general case in which a function is to be minimized and the minimum value is equality constrai ned. (C) 1998 Elsevier Science Ltd. All rights reserved.