Ultrasonic Propagation in Liquid and Ice Water Drops. Effect of Porosity.

Michiel Mendonck,Margarita G Hernández,Guillermo M Muñoz Caro,José Javier Anaya,Cristóbal González Díaz,Stéphanie Cazaux,Sofía Aparicio

doi:10.3390/s21144790

Abstract

This work studies ultrasonic propagation in liquid and ice water drops. The effect of porosity on attenuation of ultrasonic waves in the drops is also explored. The motivation of this research was the possible application of ultrasonic techniques to the study of interstellar and cometary ice analogs. These ice analogs, made by vapor deposition onto a cold substrate at 10 K, can display high porosity values up to 40%. We found that the ultrasonic pulse was fully attenuated in such ice, and decided to grow ice samples by freezing a liquid drop. Several experiments were performed using liquid or frozen water drops with and without pores. An ultrasonic pulse was transmitted through each drop and measured. This method served to estimate the ultrasonic velocity of each drop by measuring drop size and time-of-flight of ultrasonic transmission. Propagation of ultrasonic waves in these drops was also simulated numerically using the SimNDT program developed by the authors. After that, the ultrasonic velocity was related with the porosity using a micromechanical model. It was found that a low value of porosity in the ice is sufficient to attenuate the ultrasonic propagation. This explains the observed lack of transmission in porous astrophysical ice analogs.

Highlights

IntroductionComets are celestial objects formed at the outer edges of our solar system, i.e., sufficiently far away from the sun to preserve volatile species in the ice. Comets are celestial objects formed at the outer edges of our solar system, i.e., sufficiently far away from the sun to preserve volatile species in the ice
The porosity values in such ice analogs measured in the laboratory can be up to 40% for H2 O and CO2 ice [3,4] or up to 80% in water ice grown by vapor deposition at large incident angles [5]
The mean values with their standard deviations are shown in the table from which can be seen that the average ultrasonic velocity for these experiments is slightly lower than the literature values for compact water

Summary

Introduction

Comets are celestial objects formed at the outer edges of our solar system, i.e., sufficiently far away from the sun to preserve volatile species in the ice. Comets are celestial objects formed at the outer edges of our solar system, i.e., sufficiently far away from the sun to preserve volatile species in the ice This material originated in the local interstellar cloud and during the solar nebula epoch that evolved toward our current solar system. The ice mantle accretion process in space occurs by condensation of molecules onto the cold dust surfaces. At the lowest temperatures near 10 K, this accretion is expected to form highly porous ice, as occurs in laboratory simulations. This leads to a fluffy cometary ice structure since comets are made by agglomeration of icy dust particles [1,2]. The porosity values in such ice analogs measured in the laboratory can be up to 40% for H2 O and CO2 ice [3,4] or up to 80% in water ice grown by vapor deposition at large incident angles [5]

Results

Discussion

Conclusion