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Některé možnosti analytických popisů silných neadiabatických kompresí plynu
Bayer, Zdeněk
Příspěvek se zabývá modelováním stavového a termodynamického chování plynu v kavitačních bublinách. Po nedávné prezentaci modelu M3, předpokládajícího realističtější charakter výměny tepla v průběhu komprese, představuje jeho zdokonalenou verzi M4. Ukazuje, že obvykle uvažovaný polytropický model může při silných kompresích být příčinou chyb až několik desítek procent. Také dílčí výsledky předběžné analýzy vlivu zdokonalení popisu stavového chování reálného plynu vedou ke kvantitativně podobným závěrům.
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Dynamics of a bubble in variable pressure and temperature fields of a liquid
Zima, Patrik ; Maršík, František
A study of nucleation and growth of bubbles in a liquid by means of a method based on the nucleation pulse in a shock tube is proposed. The nucleation of bubbles in the shock tube is initiated by a sudden depressurization due to the expansion of the liquid. It is assumed that the nucleation is homogeneous and the nucleation rate and the growth of bubbles can be evaluated using the light scattering method. Description of the experimental setup and analytical solution of the expansion of water in a shock tube are given. The theory of radial dynamics of a spherical vapor/gas bubble in a liquid is then employed in the form of the Rayleigh-Plesset equation and some aspects of inertially controlled bubble growth are discussed. The governing equation and conditions for mass transfer across the bubble boundary due to diffusion of the contaminant gas are given.
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Nucleation and dynamics of bubbles in binary water-gas solution
Zima, Patrik ; Maršík, František
The paper deals with nucleation and dynamics of bubbles in water with dissolved contaminant gas. The nucleation model assumes binary solution of water and pure gas. Some attention is paid to the study of the effect of the dissolved gas on the onset of nucleation (cavitation). In addition, the presence of the gas component is reflected in the Rayleigh-Plesset equation, which describes the subsequent growth (and dynamics) of a bubble in a liquid. The derived equation for bubble radius assumes mass transfer across the bubble boundary, which is in the contrary to the previous and widely used assumptions of boundary impermeability and which appears to provide more realistic insights into bubble behavior. The effect of mass transfer across the bubble boundary is studied analytically and numerically. The natural frequency of the bubble is also shown for the studied problem.
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