Journal•ISSN: 0015-4628

# Fluid Dynamics

MAIK Nauka/Interperiodica

About: Fluid Dynamics is an academic journal published by MAIK Nauka/Interperiodica. The journal publishes majorly in the area(s): Boundary layer & Flow (mathematics). It has an ISSN identifier of 0015-4628. Over the lifetime, 7610 publications have been published receiving 30225 citations.

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TL;DR: In this paper, an experimental study of the stability of the interface of two gases traversed by ash-wave was conducted and it was found that the interface is unstable both in the case of shock wave passage from the lighter to the heavier gas and for passage in the opposite direction.

Abstract: Results are presented of an experimental study of the stability of the interface of two gases traversed by ashockwave. It is found that the interface is unstable both in the case of shock wave passage from the lighter to the heavier gas and for passage in the opposite direction. The interface disturbance grows linearly with time in the first approximation.

1,168 citations

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TL;DR: In this article, the phase interface in a capillary and the spreading of viscous fluid drops on solid surfaces are solved, and the dependence of this angle on the velocity with allowance for capillary forces is determined.

Abstract: Fluid motion along a smooth, solid surface is examined when the free surface forms a final visible angle with the solid boundary. The dependence of this angle on the velocity with allowance for capillary forces is determined. The Reynolds number is small. The problem of the motion of the phase interface in a capillary and the spreading of viscous fluid drops on solid surfaces are solved. Experimental results are explained. Up to now, not only were analytical results lacking in this field, but also there was not even a precise formulation of the problem (see the review in [1]).

1,074 citations

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TL;DR: In this article, the Krook model relaxation equation was used to construct a sequence of model equations which provided the correct Prandtl number for a rarefied gas, which is based on an approximation of the Boltzmann equation for pseudo-Maxwellian molecules using the method suggested by the author previously.

Abstract: One of the most significant achievements in rarefied gas theory in the last 20 years is the Krook model for the Boltzmann equation [1]. The Krook model relaxation equation retains all the features of the Boltzmann equation which are associated with free molecular motion and describes approximately, in a mean-statistical fashion, the molecular collisions. The structure of the collisional term in the Krook formula is the simplest of all possible structures which reflect the nature of the phenomenon. Careful and thorough study of the model relaxation equation [2–4], and also solution of several problems for this equation, have aided in providing a deeper understanding of the processes in a rarefied gas. However, the quantitative results obtained from the Krook model equation, with the exception of certain rare cases, differ from the corresponding results based on the exact solution of the Boltzmann equation. At least one of the sources of error is obvious. It is that, in going over to a continuum, the relaxation equation yields a Prandtl number equal to unity, while the exact value for a monatomic gas is 2/3. In a comparatively recent study [5] Holway proposed the use of the maximal probability principle to obtain a model kinetic equation which would yield in going over to a continuum the expressions for the stress tensor and the thermal flux vector with the proper viscosity and thermal conductivity. In the following we propose a technique for constructing a sequence of model equations which provide the correct Prandtl number. The technique is based on an approximation of the Boltzmann equation for pseudo-Maxwellian molecules using the method suggested by the author previously in [6], For arbitrary molecules each approximating equation may be considered a model equation. A comparison is made of our results with those of [5].

555 citations

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TL;DR: Averaged equations describing the turbulent diffusion of a chemically active admixture in coordinates tied to the instantaneous values of the concentration of another passive admixture are obtained in this article, which can be readily extended to the case of an arbitrary number of different chemically active admixtures.

Abstract: Averaged equations describing the turbulent diffusion of a chemically active admixture in coordinates tied to the instantaneous values of the concentration of another passive admixture are obtained. The results can be readily extended to the case of an arbitrary number of different chemically active admixtures. An advantage of this approach is the separation of the scales of the fluctuating and average motions, which makes the proposed average diffusion relations applicable even at times on the inertial interval.

308 citations

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TL;DR: In this paper, the authors considered the flow of a thin layer of viscous liquid (liquid film) over a solid surface as a nonlinear problem and on this basis allowed determining all the parameters of the wave regime-amplitude, wavelength, wave propagation speed, frequency.

Abstract: The studies of Kapitsa initiated the detailed experimental and theoretical study of the flow of a thin layer of viscous liquid (liquid film) over a solid surface [1–2]. Extensive experimental data on this question have now been accumulated. As a rule, the existing theories are based on linearization of the problem and diverge considerably from the experimental results. The present paper is also addressed to the theoretical solution of this problem. The solution method used enables consideration of the wave flow of the liquid as a nonlinear problem and on this basis permits determining all the parameters of the wave regime-amplitude, wavelength, wave propagation speed, frequency.

225 citations