Measurements of Cylindrical Ice Crystal Growth Limited by Combined Particle and Heat Diffusion
نویسنده
چکیده
We present measurements of the growth of long columnar ice crystals from water vapor over a broad range of temperatures and supersaturation levels in air. Starting with thin, caxis ice needle crystals, we observed their subsequent growth behavior in a vapor diffusion chamber, extracting the initial radial growth velocities of the needles under controlled conditions. Approximating the hexagonal needle crystals as infinitely long cylinders, we created an analytical growth model that includes effects from particle diffusion of water molecules through the surrounding air along with the diffusion of heat generated by solidification. With only minimal adjustment of model parameters, we obtained excellent agreement with our experimental data. To our knowledge, this is the first time that the combined effects from particle and heat diffusion have been measured in ice growth from water vapor. This analysis further provides an accurate method for calibration of the water-vapor supersaturation levels in experimental growth chambers.
منابع مشابه
The Molecular Diffusion of Ice Crystals of Various Shapes
Two main controlling factors of ice crystal growth are the heat and (gaseous) mass transfers, H&MT, as characterized by the Nusselt number (Nu) for heat and the Sherwood (Sh) number for mass. Nu and Sh express the increase of the molecular diffusions by the relative motions of the particles in air as characterized by the Reynolds number (Re). Traditionally Nu is assumed to be identical to Sh. P...
متن کاملThe physics of snow crystals
We examine the physical mechanisms governing the formation of snow crystals, treating this problem as a case study of the dynamics of crystal growth from the vapour phase. Particular attention is given to the basic theoretical underpinnings of the subject, especially the interplay of particle diffusion, heat diffusion and surface attachment kinetics during crystal growth, as well as growth inst...
متن کاملOn the Formation of Thin Ice Crystal Plates: A New Type of Morphological Instability in Diffusion-Limited Growth
We propose a new type of morphological instability in the diffusion-limited growth of faceted crystals from the vapor phase that can explain the formation of thin ice plates at temperatures near -15 C. The instability appears when the attachment kinetics for facet growth depends strongly on the morphology of the facet surface. In particular, we propose that the condensation coefficient for grow...
متن کاملExplaining the formation of thin ice crystal plates with structure-dependent attachment kinetics
We propose a new type of crystal growth phenomenon—structure-dependent attachment kinetics—to explain the growth of thin ice plates from the vapor phase at temperatures near 15 C. In particular, we propose that the condensation coefficient for growth of ice prism facets increases dramatically when the width of the facet approaches atomic dimensions. This model reconciles several conflicting mea...
متن کاملIce crystals growing from vapor in supercooled clouds between −2.5 and −22C: testing current parameterisation methods using laboratory data
The physical and empirical relationships used by microphysics schemes to control the rate at which vapor is transferred to ice crystals growing in supercooled clouds are compared to laboratory data to evaluate the realism of various model formulations. Ice crystal growth rates predicted from capacitance theory are compared to measurements from three independent laboratory studies. When the grow...
متن کامل