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Polynomial approximations of thermodynamic properties of arbitrary gas mixtures over wide pressure and density rangesComputer programs for flow fields around planetary entry vehicles require real-gas equilibrium thermodynamic properties in a simple form which can be evaluated quickly. To fill this need, polynomial approximations were found for thermodynamic properties of air and model planetary atmospheres. A coefficient-averaging technique was used for curve fitting in lieu of the usual least-squares method. The polynomials consist of terms up to the ninth degree in each of two variables (essentially pressure and density) including all cross terms. Four of these polynomials can be joined to cover, for example, a range of about 1000 to 11000 K and 0.00001 to 1 atmosphere (1 atm = 1.0133 x 100,000 N/m sq) for a given thermodynamic property. Relative errors of less than 1 percent are found over most of the applicable range.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Allison, D. O.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 2, 2013
Publication Date
August 1, 1972
Subject Category
Thermodynamics And Combustion
Report/Patent Number
Accession Number
Funding Number(s)
PROJECT: RTOP 501-06-01-02
Distribution Limits
Work of the US Gov. Public Use Permitted.
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