Diffusion Stability of Mechanical Equilibrium in Compressible Isothermal Gases
— This paper is presented stability condition of mechanical equilibrium for diffusion of compressible isothermal gases in a cylindrical domain. Two general cases of the divergent stable motions were considered when density depended on the conditions 0  u div  and 0  u div . Stability criterion of mechanical equilibrium for the compressible gas mixture is proposed by defining continuous dependence of the velocity vector for the compressible flows in the Navier-Stokes problem from initial date. Using the parametrix method of theory nonlinear partial differential equations were obtained the velocity components for the transient compressible flows. Introduced stability condition for isothermal gases was predicted in the principal form by the energy conservation law and based on the transport equation for an appropriate convergent-divergent turbulent gas motion.
Study of Diffusion Instability in Some Ternary Gas Mixtures at Various Temperatures
Within the linear theory of stability, the process of isothermal mixing of three-component gas mixtures in a channel of final dimensions in the absence of mass-transfer through its walls is considered. The comparison of experimental data with the results of theoretical calculations for the mixtures He+Ar-N2 and H2+N2-CH4 is shown, that a stable diffusion process as the temperature increased will remain the same and be described by the ordinary diffusion laws, but unstable one lost its intensity and tend to the stable diffusion.
The micro-mechanical behaviour of artificially cemented sand particles under compression and shear
The mechanical behaviour of cemented sands at macro-scale has been widely studied in the past, while there is still a lack of laboratory test data for the micro-mechanical response. Therefore, a series of uniaxial compression and tangential shear tests on artificially cemented sand particles have been conducted using a microscope to observe their behaviour. First, the consistency of cemented particles with different cementing agents is discussed. Three breakage modes are proposed according to the images taken using a microscope camera. A new parameter named ‘local roundness at contact’ is introduced to emphasise the effect of contact morphology on sample strength. Moreover, the effect of bond thickness on the mechanical response of cemented particles has been investigated. Finally, the shear strength parameters of artificially cemented sand samples have been determined for two different sample diameters.