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THE EFFECTS OF THE MOLECULAR PROPERTIES OF AN INJECTED GAS ON COMPRESSIBLE AIR LAMINAR BOUNDARY LAYER SKIN FRICTION AND HEAT TRANSFER
NAVAL ORDNANCE LAB WHITE OAK MD
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A theoretical study has been made on the effects of the molecular properties of a gas injected into the compressible air laminar boundary layer on a flat plate. A simple rigid sphere model was used for describing the transport properties of viscosity, thermal conductivity, and diffusion coefficient, requiring knowledge only of molecular weight and molecular or collision diameter. The specific heat was computed from the equipartition of energy. The analysis demonstrated that small molecular eight and l rg molecular diameter were desirable for the reduction of skin friction a heat transfer. Furthermore, large specific heat per unit mass reduce heat transfer but had little effect on skin friction. Large specific heat on a unit mass basis may result from either low molecular weight as in the case of helium or high molar specific heat as in the case of polyatomic gases which have many internal degrees of freedom. The combination of large molecular diameter and large molar specific heat associated with a polyatomic gas may be more significant in reducing skin friction and heat transfer than the low molecular weight of a monatomic gas like helium. Author
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