Discretization Errors in the Far Field Conditions for Oscillatory Subsonic Flows

Item

Title
Discretization Errors in the Far Field Conditions for Oscillatory Subsonic Flows
Date
1981
Index Abstract
Coming Soon
Photo Quality
Not Needed
Report Number
AFWAL TR 81-3150
Corporate Author
University of Dayton Research institute
Date Issued
1981-12-01
Extent
66
Identifier
ADA110995
Distribution Classification
1
Contract
AFOSR 78-3524
DoD Project
2304
DoD Task
2304N1
DTIC Record Exists
No
Distribution Change Authority Correspondence
None
Abstract
In their complete form, far field conditions are given by an infinite number of global linear equations between the potential and its normal derivative at the far boundary of the computed part of a flow field. This report illustrates the effects of a discretization carried out in the partial differential equation for different formulations of the far field conditions. If one considers the potential and its normal derivative at all points of the far boundary as infinite vectors, then the far field conditions are established by the infinite matrices. The appearance of these matrices depends upon the choice of the 'test' functions used in formulating the far field conditions, but the relations obtained for different formulations arise from each other by premultiplication with some matrix. In a numerical approach an approximation of the potential and its normal derivative in terms of a finite number of parameters must be used, the vector is restricted to a finite dimensional subspace. The matrices encountered in formulating the far field conditions depend upon the choice of the subspace and of the relative eigenvectors and eigenvalues of the two matrices. For vectors in an infinite vector space they are independent of the choice of the test functions. The effect of the discretization can be recognized by the deviation of the eigenvectors and eigenvalues from the ideal case.
Report Availability
Full text available by request
Provenance
IIT
Type
report
Format
66 pages ; 28 cm.
Creator
Guderly, K. G.