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The role of impurities in cavitation-threshold determination
The r o l e of i m p u r R i e s in cavitation-threshold determination Appel, R. E. Vol 48, No 5 (November 1970) pp1179-1186 We have extended the t h e o r e t i c a l work of H a r v e y et al (1944) and S t r a s b e r g (1959} in o r d e r to consider the conditions that must exist in a liquid for a vapour cavity to be nucleated f r o m an i m p e r f e c t l y wetted solid impurity (mote) in the liquid. It is found that, for sufficiently s m a l l and readily wetted motes, the tensile s t r e s s r e q u i r e d for nucleation i n c r e a s e s with i n c r e a s i n g s u r f a c e tension and d e c r e a s i n g mote size but is almost independent of the gas content and h i s t o r y of the liquid. On the other hand for sufficiently large and i m p e r f e c t l y wetted motes, the gas content of the liquid and its h i s t o r y are crucial, w h e r e a s the mote size and the liquid-vapour surface tension play no role in determining the conditions for nucleation. The qualitative prediction of this theory of moteinduced nucleation bring some semblance of order to a wide variety of observations of statically induced cavitation az~d low-frequency acoustic cavitation reported in the literature. Measurement of the effect of air bubbles on the speed of sound in water Gibson, F. W. Vet 48, No 5 (November 1970) pp1195-1197 A simple technique for m e a s u r i n g the effect of air bubbles on the speed of sound in water, and hence on the attenuation of p r e s s u r e pulses in water, has been developed. The good a g r e e m e n t of the e x p e r i m e n t a l data with computed values indicates the adequacy of the experimental method. The c h a r a c t e r i s t i c s of the acoustical pulses emitted by boiling bubbles in water Saxe, R. F., Cothren, R. K. Vol 48, No 5 (November 1970) pp1257-1265 An investigation of the acoustic e m i s s i o n s f r o m boiling bubbles in water has been made using two methods--frequency analysis and pulse-height analysis. P u l s e - h e i g h t analysis, using coincidence techniques, shows that the pulse-height s p e c t r u m of boiling bubbles in water has a distribution which is independent of the amount of boiling, indicating that the distribution is governed by liquid, vapour, and possible w i r e - s u r f a c e c h a r a c t e r i s t i c s . The addition of wetting agent to the water has an appreciable effect on the pulse-height distribution. Frequency analysis is shown to produce no information about pulse c h a r a c t e r istics.
Temperature dependence of the ultrasonic velocity in cyelohexane Taylor, E. W., Alpert, S. S. Vol 48, No 5 (November 1970) pp1287-1288 The velocity of 1 8 M H z ultrasound in cyclohexane as a function of t e m p e r a t u r e was m e a s u r e d by Bragg diffraction of l a s e r light. The adiabatic c o m p r e s s ibility was calculated f r o m these m e a s u r e m e n t s .
confidence in their use for acoustic waveguide mode analysis. Sound channels in s u r f i c i a l marine sediments Hamilton, E. L. Vol 48, No 5 (November 1970) pp1296-1298 Most d e e p - s e a s i l t - c l a y surficial sediments have sound velocities less than that in the water overlying the bottom. T h e s e sediment velocities, b o t t o m - w a t e r velocities, and r e c e n t l y established s e d i m e n t - v e l o c i t y gradients, define a sound channel in surficial sediments which should be p r e s e n t in most d e e p - s e a floors, and in some shallow-water a r e a s . The height of these sound channels in deep water should n o r m a l l y v a r y between 15 and 60m. A novel technique for measuring the strength of liquids Appel, R. E. Vol 49, No 1 (January 1971) pp145-155 A novel technique has been effectively utilized in studying the properties of liquids under conditions that are not ordinarily accessible. This technique involves the use of an acoustic standing-wave field established in a column of one liquid in order to trap in immiscible droplet of another liquid. In the experiment reported here, a filtered ether droplet suspended in filtered glycerine was superheated and acoustically stressed until the combination produced an explosive liquid-to-vapor phase transition. The experiment was performed under atmospheric conditions at which the normal boiling point of ether is 35.6°C. The measured tensile strength varied linearly from 17 bars at 130 °C to 0 bars at 146[]C. Previous measurements of the tensile strength of liquids have not come within a factor of 2 or 3 of the theoretical predictions based on homogenous nucleation theory, a theory which describes the vapourization conditions for pure liquid. The results reported here axe in good agreement with that theory. This novel agreement is attributed to the ability to obtain pure liquid samples by utilizing small (0.5ram dicta) filtered droplets.
Spectral analysis of cavitation noise in cryogenic
liquids Mosse, A., Finch, R. D. Vol 49, No 1 (January 1971} pp156-165 Spectra of ultrasonic cavitationnoise were obtained in liquid helium and liquid nitrogen. A subharmonic response at half the driving frequency was found to be p r e s e n t at all times. In the case of liquid helium, the relative intensity of this subharmonic showed a peak. The background noise intensity was also higher in helium II. A tendency for the h a l f - o r d e r subharmonic to i n c r e a s e with static p r e s s u r e was also found both for helium I and nitrogen. A c o r r e l a t i o n between the onset of the subharmonic audible-frequency noise and the white-noise background was also found. The variation of the intensity of the f i r s t overtone with i n c r e a s i n g driving voltage was found to be different in helium II than in other liquids. It is argued that many of these phenomena arise f r o m the effect on bubble dynamics of the efficient heat t r a n s p o r t in helium II.
Sound-speed dispersion in liquid cylinders Del Grosso, V. A., McGilI, R. E. Vet 48, No 5 (November 1970) pp1294-1296 An inversion of the ordinate in the usual plot of the d i s p e r s i o n c u r v e s for axial acoustic propagation in liquid cylinders p e r m i t s t r a c k i n g of modes f r o m their evanescent region for p r o p e r ordering, and g r e a t e r
Effects of input amplitude profile upon diffraction t o s s and phn~e change in a p u l s e - e c h o s y s t e m Papadakis, E. 19. Yol 49, No 1 (January 1971) pp166-168 The particle velocity profile V(p} a c r o s s the face of a t r a n s m i t t i n g t r a n s d u c e r is shown to have large ULTRASONICS July 1971
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Temperature dependence of the ultrasonic velocity in cyelohexane Taylor, E. W., Alpert, S. S. Vol 48, No 5 (November 1970) pp1287-1288 The velocity of 1 8 M H z ultrasound in cyclohexane as a function of t e m p e r a t u r e was m e a s u r e d by Bragg diffraction of l a s e r light. The adiabatic c o m p r e s s ibility was calculated f r o m these m e a s u r e m e n t s .
confidence in their use for acoustic waveguide mode analysis. Sound channels in s u r f i c i a l marine sediments Hamilton, E. L. Vol 48, No 5 (November 1970) pp1296-1298 Most d e e p - s e a s i l t - c l a y surficial sediments have sound velocities less than that in the water overlying the bottom. T h e s e sediment velocities, b o t t o m - w a t e r velocities, and r e c e n t l y established s e d i m e n t - v e l o c i t y gradients, define a sound channel in surficial sediments which should be p r e s e n t in most d e e p - s e a floors, and in some shallow-water a r e a s . The height of these sound channels in deep water should n o r m a l l y v a r y between 15 and 60m. A novel technique for measuring the strength of liquids Appel, R. E. Vol 49, No 1 (January 1971) pp145-155 A novel technique has been effectively utilized in studying the properties of liquids under conditions that are not ordinarily accessible. This technique involves the use of an acoustic standing-wave field established in a column of one liquid in order to trap in immiscible droplet of another liquid. In the experiment reported here, a filtered ether droplet suspended in filtered glycerine was superheated and acoustically stressed until the combination produced an explosive liquid-to-vapor phase transition. The experiment was performed under atmospheric conditions at which the normal boiling point of ether is 35.6°C. The measured tensile strength varied linearly from 17 bars at 130 °C to 0 bars at 146[]C. Previous measurements of the tensile strength of liquids have not come within a factor of 2 or 3 of the theoretical predictions based on homogenous nucleation theory, a theory which describes the vapourization conditions for pure liquid. The results reported here axe in good agreement with that theory. This novel agreement is attributed to the ability to obtain pure liquid samples by utilizing small (0.5ram dicta) filtered droplets.
Spectral analysis of cavitation noise in cryogenic
liquids Mosse, A., Finch, R. D. Vol 49, No 1 (January 1971} pp156-165 Spectra of ultrasonic cavitationnoise were obtained in liquid helium and liquid nitrogen. A subharmonic response at half the driving frequency was found to be p r e s e n t at all times. In the case of liquid helium, the relative intensity of this subharmonic showed a peak. The background noise intensity was also higher in helium II. A tendency for the h a l f - o r d e r subharmonic to i n c r e a s e with static p r e s s u r e was also found both for helium I and nitrogen. A c o r r e l a t i o n between the onset of the subharmonic audible-frequency noise and the white-noise background was also found. The variation of the intensity of the f i r s t overtone with i n c r e a s i n g driving voltage was found to be different in helium II than in other liquids. It is argued that many of these phenomena arise f r o m the effect on bubble dynamics of the efficient heat t r a n s p o r t in helium II.
Sound-speed dispersion in liquid cylinders Del Grosso, V. A., McGilI, R. E. Vet 48, No 5 (November 1970) pp1294-1296 An inversion of the ordinate in the usual plot of the d i s p e r s i o n c u r v e s for axial acoustic propagation in liquid cylinders p e r m i t s t r a c k i n g of modes f r o m their evanescent region for p r o p e r ordering, and g r e a t e r
Effects of input amplitude profile upon diffraction t o s s and phn~e change in a p u l s e - e c h o s y s t e m Papadakis, E. 19. Yol 49, No 1 (January 1971) pp166-168 The particle velocity profile V(p} a c r o s s the face of a t r a n s m i t t i n g t r a n s d u c e r is shown to have large ULTRASONICS July 1971
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