Numerical and Experimental Investigations of Thermal Stress Effect on Nonlinear Thermomolecular Pressure Difference

Abstract

Investigation of slow nonisothermal gas flow is continued. The problem of nonlinear thermomolecular pressure difference at the ends of capillary is considered. This pressure difference originates from temperature difference at the ends of capillary under any flow regime. Gas flow in cylindrical capillary is numerically investigated in continuum regime. In this case the slow nonisothermal flow equations and Navier‐Stokes equations are used. Slow nonisothermal flow equations are the generalization of Navier‐Stokes equations, taking into account temperature stress action in the bulk of a gas. Numerical investigation are carried out for two dependence of viscosity coefficient on temperature, ‐ linear and square root. These dependences agree with soft potential (Maxwell molecules) and stiff potential (hard sphere molecules) of molecular interaction. Temperature boundary distribution corresponds to experimental conditions. The correlation parameter is found. The numerical investigation of flow in plane channel is carried out for kinetic (transition) regime. The limits of applicability (on small values of Knudsen number) for slow nonisothermal flow equations are numerically determined. Experimental investigation of differential nonlinear thermomolecular pressure difference is carried out on special facility. The flows of monatomic gases (helium, argon) and diatomic gases (nitrogen, air) are investigated. Qualitative correlation between theoretical and experimental data is established. Correlation of the data for monatomic gases is possible by Knudsen number. Inapplicability of Navier‐Stokes equations for investigation of slow gas flows under strong heat transfer is confirmed. The quantitative agreement of numerical and experimental data for helium is shown.