Flow of a slightly rarefied gas in a narrow slit channel in the case of sublimation from one of the walls and heat inflow from the other

1975 ◽  
Vol 28 (1) ◽  
pp. 32-39
Author(s):  
P. A. Novikov ◽  
L. Ya. Lyubin ◽  
V. I. Balakhonova
Keyword(s):  
Rarefied Gas ◽  
The Other ◽  
Narrow Slit ◽  
Slit Channel ◽  
Heat Inflow ◽  
Slightly Rarefied Gas

scholarly journals The scattering of α-particles by matter

1910 ◽  
Vol 83 (565) ◽  
pp. 492-504 ◽  
Keyword(s):  
Quantitative Measurement ◽  
Direct Evidence ◽  
Zinc Sulphide ◽  
The Other ◽  
Narrow Slit ◽  
Preliminary Note ◽  
Metal Foils ◽  
Strong Source ◽  
Α Particles

In a preliminary note (‘Roy. Soc. Proc.’ A, vol. 81, p. 174, 1908) on the above subject, experiments were described which gave direct evidence of the scattering of the α -particles. In those experiments a strong source of α -radiation was placed at one end of a long exhausted tube, and the α -particles, after passing through a narrow slit, fell upon a zinc sulphide screen sealed to the other end of the tube. When the pressure inside the tube was very low, the narrow line of scintillations which marked the place of incidence of the α -particles on the screen was well defined, but when the rays on their way to the screen passed through gas or through thin metal foils the edges of this line of scintillations became indistinct. The amount of scattering could be estimated for different foils by placing them in the path of the rays and noting the distribution of the scintillations on the screen. The present investigation was undertaken with a view to obtain a quantitative measurement of the scattering by determining the most probable angle through which an α -particle of definite range is turned by passing through a given thickness of matter. The following are the chief points investigated:— (1) Determination of the amount of scattering produced in different thicknesses of the same material. (2) Comparison of the amounts of scattering produced in different materials. (3) Relation between the velocity of the α -particles and the amount of their scattering.

Axisymmetric thermal-creep flow of a slightly rarefied gas induced around two unequal spheres

1984 ◽  
Vol 144 ◽  
pp. 103-121 ◽  
Author(s):  
Yoshimoto Onishi
Keyword(s):  
Reynolds Number ◽  
Temperature Gradient ◽  
Rarefied Gas ◽  
Low Reynolds Number ◽  
Thermal Creep ◽  
Creep Flow ◽  
Low Reynolds ◽  
Thermal Creep Flow ◽  
Slightly Rarefied Gas ◽  
Thermal Conductivities

A thermal-creep flow of a slightly rarefied gas induced axisymmetrically around two unequal spheres is studied on the basis of kinetic theory. The spheres, whose thermal conductivities are assumed to be identical with that of the gas, for simplicity, are placed in an infinite expanse of the gas at rest with a uniform temperature gradient at a far distance. Owing to the poor thermal conductivities of the spheres, a tangential temperature gradient is established on the surfaces, and this causes a thermal-creep flow in its direction. Consequently, the spheres experience forces in the opposite direction.The flow considered here is a low-Reynolds-number flow in the ordinary fluid-dynamic sense (except for the Knudsen layer), and the solution is obtained in terms of bispherical coordinates, with respect to which the system of equations of Stokes type is well developed. The velocity field around the spheres and the forces acting on them are given explicitly. The results show the interesting feature that the smaller sphere experiences the minimum force at a value of the separation distance that depends on the radius ratio. This is in contrast with the case of the axisymmetric motion of two spheres treated by Stimson & Jeffery (1926) in ordinary fluid dynamics at low Reynolds number.The ultimate velocities that the spheres would have under the action of the present thermal force when they are freely suspended are also obtained by utilizing the results for the forces of axisymmetric translational problems of two spheres at low Reynolds number. For a given temperature gradient in the gas, both spheres acquire larger velocities than those they would have if they were alone, and the smaller sphere tends to move faster than the larger one in the direction opposite to the temperature gradient.Also presented, for completeness, are the results for the sphere–plane case and for the case of eccentric spheres, the solutions for which are derived as special cases of the preceding problem of two unequal spheres.

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