A tractable method for estimating atomic and molecular transport coefficients
| Autor: | R. S. Bernard, R. L. Fox |
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| Rok vydání: | 1970 |
| Předmět: | |
| Zdroj: | AIAA Journal. 8:2085-2086 |
| ISSN: | 1533-385X 0001-1452 |
| Popis: | O calculate the flow in the vicinity of an ablating or transpiration cooled surface, one often requires the values of the transport coefficients of the various species injected into the boundary layer. Sufficient experimental data does not exist to obtain parameters needed for a semiempirical determination of these transport coefficients. A method of obtaining transport coefficients without recourse to experimental data would thus be of great value. Such methods have been studied in the past by other investigators.1 The purpose of this Note is to present a method of calculating transport coefficients, which is simple enough to be carried out quickly and without the use of a computer. Comparison of transport coefficients obtained using this method with experimental data show agreement which is generally as good as those obtained from more elaborate computation. The interaction between two neutral molecules is taken to be of the form of a dispersion potential V(r) = — A/r*,2a where r is the interparticle separation, and A is a constant for a given set of molecules. The apparent collision radius for the interaction is obtained by letting the potential be proportional to the gas temperature T. The constant of proportionality has previously been studied,3 where it has been shown that transport coefficients depend weakly on the proportionality constant. As shown below, the present method is independent of the proportionality constant, but introduces another parameter which will be discussed later. It is assumed that for some gas temperature TI the collision radius equals the root mean square radius of the outer shell electrons in the molecule, rms. With this assumption, the collision cross section |
| Databáze: | OpenAIRE |
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