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numerical-accuracy
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General solution of linear differential equations by using differential transfer matrix method
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 3 , 2005 , Pages 113-116 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2005
Abstract
A new analytical method for finding the general solution of the nth-order linear differential equation with variable coefficients is given based on generalizing the idea of differential transfer matrix method already proposed for solving the second order Helmholtz equation. Our generalization has two aspects. First, the given formulation copes with the nth-order linear differential equations, rather than the special case of second order wave equations. Second, the proposed approach is generalized in several different ways each yielding different types of differential transfer matrices with correspondingly different numerical accuracies. The presented methods can be applied to problems such...
Exhaust soot investigation in a JP combustor working at various wall temperatures
, Article AIAA Aerospace Sciences Meeting, 2018, 8 January 2018 through 12 January 2018 ; Issue 210059 , 2018 ; 9781624105241 (ISBN) ; Ghafourizadeh, M ; Darbandi, M ; Saidi, M. H ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc, AIAA
2018
Abstract
In this study, a jet propulsion JP combustor is studied numerically to investigate the combustor wall temperature influences on the soot characteristics emitted at its exhaust. There are a number of ways to control the combustor wall temperatures benefiting from different wall cooling technologies. Irrespective of using different high technology cooling systems, it is important to recognize how the wall temperature can affect the soot emission from one specific JP engine. Before examining the main combustor, it is important to assess the accuracy of the computational fluids dynamics (CFD) tool via solving a benchmark problem. In this regard, the predicted flame structure for the benchmark...
Effect of different geometries in simulation of 3D viscous flow in francis turbine runners
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 363-369 ; 10263098 (ISSN) ; Dadfar, R ; Pirali, A. P ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
Overall turbine analysis requires large CPU time and computer memory, even in the present days. As a result, choosing an appropriate computational domain accompanied by a suitable boundary condition can dramatically reduce the time cost of computations. This work compares different geometries for numerical investigation of the 3D flow in the runner of a Francis turbine, and presents an optimum geometry with least computational effort and desirable numerical accuracy. The numerical results are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on 3D computation of incompressible internal flows, 1989) in which the geometry and detailed best efficiency...