1. n. [Enhanced Oil Recovery]
A standard laboratory instrument to measure interfacial tension. The method is particularly applicable to values of interfacial tension below 1 mN/m and especially below 10-2 mN/m, as may occur when employing surfactants for enhanced oil recovery. The method utilizes a tube containing a drop of the less-dense phase within the more-dense phase. When the tube is spun along its long axis at high speed, the resulting forces center the drop on the tube axis and deform it. The interfacial tension is a function of the shape of the deformed drop, the liquid densities and the rotation speed. Advanced versions of the instrument can periodically vary the rotation rate. The phase lag between the change of rotation rate and the drop deformation can be used to determine both interfacial elasticity and interfacial viscosity.
