Unsteady heat transfer of a monatomic gas between two coaxial circular cylinders
We consider a kinetic-theory treatment of the cylindrical unsteady heat transfer. A model kinetic equation of the BGK (Bhatnager-Gross-Krook) type is solved using the method of moments with a two-sided distribution function. We study the relations between the different macroscopic properties of the gas as the temperature, density, and heat flux with both the radial distance r and the time t. Also we study the problem from the viewpoint of irreversible thermodynamics and estimate the entropy, entropy production, entropy flux, thermodynamic forces, kinetic coefficients, the change in internal energy, and verify Onsager′s relation for nonequilibrium thermodynamic properties of the system.
Numerical solution of a kinetic equation for the evaporation-condensation problem
A problem of a steady radial gas flow between two infinitely long coaxial cylinders with the boundary conditions of evaporation (emission) and condensation (absorption) is formulated for a nonlinear kinetic equation with a model operator of collisions. This problem is solved by the finite difference method. A numerical algorithm with the separation of the discontinuities of the distribution function is constructed. The effect of discontinuities on the accuracy of the solution is studied. Considerable attention is paid to the study of the flow from the inner evaporation cylinder to the absolutely absorbent outer one. The removal of the outer cylinder results in the limit mode of the flow.
Kinemamtic analysis of flying-saw vehicle
The paper analyzes the kinematic motion of the flying-saw vehicle.After the analysis,it is concluded that the ac- celerating periods and decelerating periods in both forward and backward directions will follow sin~2αcurve and,in order to increase the sawing dimensional accuracy,flying-saw vehicle must come back as soon as possible while acceleration remains constant.Based on this premise,the paper gives out the equations of kinematic motion of the flying-saw vehicle in every sta- ges and one example result in a common situation.By now this method has been used in the real situation.