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RE Apfel

Publications and source records attributed to RE Apfel.

6 recordsLinked to original sources
PubMed2000

Extensive experimental mapping of sonoluminescence parameter space

Experimental phase diagrams are compared to theoretical predictions based on the Dissociation Hypothesis (DH) theory of single bubble sonoluminescence (SBSL). Ambient radius (R(o))- acoustic drive pressure (P(a)) phase diagrams are presented for krypton-nitrogen mixtures and for a collection of data with other noble gas-nitrogen mixtures. The data is also presented in terms of expansion ratio (maximum bubble radius R(max)/R(o)) vs P(a) and relative light intensity vs P(a). The results provide further evidence of the validity of DH and also provide a thorough mapping of SBSL at a single frequency.

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PubMed2000

Using phase space diagrams to interpret multiple frequency drive sonoluminescence

The recent experimental results of J. Holzfuss, M. Ruggeberg, and R. Mettin [Phys. Rev. Lett. 81, 1961 (1998)] in which a second harmonic drive system was used to generate sonoluminescence (SL) have been analyzed in the context of the dissociation hypothesis (DH) of D. Lohse and S. Hilgenfeldt [J. Chem. Phys. 107, 6986 (1997)]. The second harmonic introduces two more variables that are under experimental control: a phase and an additional pressure term to the acoustic drive pressure. Diffusive equilibrium curves for a fixed gas concentration were calculated as was the Mach criterion. A phase space diagram was constructed to permit the prediction of regions of stable SL, unstable SL, stable non-SL, and unstable non-SL. These were compared to Holzfuss' experimental observations, and excellent quantitative agreement was seen. The results provide further evidence that the underlying assumptions of DH are sound. They also indicate the utility of DH for determining appropriate experimental conditions to achieve SL and for optimizing an experimental system.

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PubMed1997

Investigation of Liquid Surface Rheology of Surfactant Solutions by Droplet Shape Oscillations: Experiments

The experimental results of droplet shape oscillations are reported and applied to the analysis of surface rheological properties of surfactant solutions. An acoustic levitation technique is used to suspend the test drop in air and excite it into quadrupole shape oscillations. The equilibrium surface tension, Gibbs elasticity, and surface dilatational viscosity are determined from the measurements of droplet static shape under different levitation sound pressure, oscillation frequency, and free damping constant. Aqueous solutions of sodium dodecyl sulfate, dodecyltrimethylammonium bromide, and n-octyl beta-d-glucopyranoside are tested with this system. The concentrations of the solutions are below the critical micelle concentration. For these solutions it is found that the surface Gibbs elasticity approaches a maximum at a moderate concentration, and its value is less than that directly calculated from the state equation of a static liquid surface. The surface dilatational viscosity is found to be in a range around 0.1 cps.

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