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The spatially nonuniform convergence of the numerical solution of flowsThe spatial distribution of the numerical disturbances that are generated during the numerical solution of a flow is examined. It is shown that the distribution of the disturbances is not uniform. In regions where the structure of a flow is simple, the magnitude of the generated disturbances is small and their decay is fast. However, in complex flow regions, as in separation and vortical areas, large magnitude disturbances appear and their decay may be very slow. The observed nonuniformity of the numerical disturbances makes possible the reduction of the calculation time by application of what may be called the partial-grid calculation technique, in which a major part of the calculation procedure is applied in selective subregions, where the velocity disturbances are large, and not within the whole grid. This technique is expected to prove beneficial in large-scale calculations such as the flow about complete aircraft configurations at high angle of attack. Also, it has been shown that if the Navier-Stokes equations are written in a generalized coordinate system, then in regions in which the grid is fine, such as near solid boundaries, the norms become infinitesimally small, because in these regions the Jacobian has very large values. Thus, the norms, unless they are unscaled by the Jacobians, reflect only the changes that happen at the outer boundaries of the computation domain, where the value of the Jacobian approaches unity, and not in the whole flow field.
Document ID
19880002047
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Panaras, Argyris G. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 5, 2013
Publication Date
November 1, 1987
Subject Category
Numerical Analysis
Report/Patent Number
A-88016
NAS 1.15:100037
NASA-TM-100037
Accession Number
88N11429
Funding Number(s)
PROJECT: RTOP 505-60
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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