Capillary waves maximum damping

Fig. 4 General solution for the dispersion equation on water at 25 °C. The damping coefficient a vs. the real capillary wave frequency o> , for isopleths of constant dynamic dilation elasticity ed (solid radial curves), and dilational viscosity k (dashed circular curves). The plot was generated for a reference subphase at k = 32431 m 1, ad = 71.97 mN m-1, /i = 0mNsm 1, p = 997.0kgm 3, jj = 0.894mPas and g = 9.80ms 2. The limits correspond to I = Pure Liquid Limit, II = Maximum Velocity Limit for a Purely Elastic Surface Film, III = Maximum Damping Coefficient for the same, IV = Minimum Velocity Limit, V = Surface Film with an Infinite Lateral Modulus and VI = Maximum Damping Coefficient for a Perfectly Viscous Surface Film...

One area where SQELS can make a significant contribution is that of polymers at liquid/liquid interfaces. Since the viscosity and density of the two fluids are much closer the coupling between dilation and capillary waves is severely attenuated and the prospects for obtaining dilational modulus and viscosity are much reduced or nonexistent. Oil/water interfaces are particularly interesting when block copolymers are placed at the interface. Only one such system has so far been discussed a block copolymer of styrene and ethylene oxide was placed at the interface between heptane and water (Sauer et al. 1987). There appears to be some evidence of a maximum in the damping of the interfacial capillary waves as the concentration of copolymer was increased. 

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