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On the Divergence of the Velocity Vector in Real-Gas FlowA theoretical study was performed addressing the degree of applicability or inapplicability, to a real gas, of the occasionally stated belief that for an ideal gas, incompressibility is synonymous with a zero or very low Mach number. The measure of compressibility used in this study is the magnitude of the divergence of the flow velocity vector [V(bar) (raised dot) u (where u is the flow velocity)]. The study involves a mathematical derivation that begins with the governing equations of flow and involves consideration of equations of state, thermodynamics, and fluxes of heat, mass, and the affected molecular species. The derivation leads to an equation for the volume integral of (V(bar) (raised dot) u)(sup 2) that indicates contributions of several thermodynamic, hydrodynamic, and species-flux effects to compressibility and reveals differences between real and ideal gases. An analysis of the equation leads to the conclusion that for a real gas, incompressibility is not synonymous with zero or very small Mach number. Therefore, it is further concluded, the contributions to compressibility revealed by the derived equation should be taken into account in simulations of real-gas flows.
Document ID
20090035882
Acquisition Source
Jet Propulsion Laboratory
Document Type
Other - NASA Tech Brief
External Source(s)
http://www.techbriefs.com/component/content/article/5789
Authors
Bellan, Josette (California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
October 1, 2009
Publication Information
Publication: NASA Tech Briefs, October 2009
Subject Category
Technology Utilization And Surface Transportation
Report/Patent Number
NPO-46113
Distribution Limits
Public
Copyright
Public Use Permitted.

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