EFFECTIVE VISCOSITIES OF A PHASE-SEPARATING BINARY MIXTURE IMPOSED TOSHEAR

We report measurements of effective viscosities in a near-critical pha se separating binary mixture in the presence of a how field. Our exper imental results suggest that the viscosity associated with a Bow-induc ed quasi-stationary, two-phase structure obeys Onuki's formula, in whi ch a delicate balance between shear and growing domains should be achi eved, resulting in significantly extended domain structures in the flo w direction. It is observed that the domains break up into spherical o nes smaller in size than those in a quiescent mixture when the shear i s turned off. This implies that the undulation associated with a tube- like concentration domain could be suppressed by shear. (C) 1998 Publi shed by Elsevier Science B.V.