Heavy gas mixtures for wind tunnels.

The subject of this thesis is to use the kinetic theory of gases to predict the optimum choice of a heavy-gas mixture as a possible alternative to air as a test medium in wind-tunnels through which the power requirements and size-scale factors can be minimised. The Wilke viscosity approximation, which is based on the mean-free-path method is used as the basis for this work because of its reasonable agreement with experiment. The power-saving and scale-size reduction in wind-tunnels are improved for gases with lower viscosity. The general conditions for which a mixture viscosity can be lower (or higher) than the simple average of pure-gas viscosities are obtained and applied to a number of actual gas mixtures. Calculations of the power-saving and size-scale factors have been performed for any polyatomic gas, when it is mixed with a specified heavy monatomic gas, under test conditions of known mass, viscosity and specific heat while maintaining the condition that the specific heat ratio is equal to that of air. The results are presented graphically together with relevant specimen studies and a review of the related background