Overview of the 2018 Workshop on Iterative Errors in Unsteady Flow SimulationsSource: Journal of Verification, Validation and Uncertainty Quantification:;2020:;volume( 005 ):;issue: 002::page 021006-1Author:Eça, L.
,
Vaz, G.
,
Hoekstra, M.
,
Pal, S.
,
Muller, E.
,
Pelletier, D.
,
Bertinetti, A.
,
Difonzo, R.
,
Savoldi, L.
,
Zanino, R.
,
Zappatore, A.
,
Chen, Y.
,
Maki, K. J.
,
Ye, H.
,
Drofelnik, Jernej
,
Moss, Benjamin
,
Da Ronch, Andrea
DOI: 10.1115/1.4047922Publisher: The American Society of Mechanical Engineers (ASME)
Abstract: Two workshops were held at the ASME V&V Symposiums of 2017 and 2018 dedicated to Iterative Errors in Unsteady Flow Simulations. The focus was on the effect of iterative errors on numerical simulations performed with implicit time integration, which require the solution of a nonlinear set of equations at each time-step. The main goal of these workshops was to create awareness to the problem and to confirm that different flow solvers exhibited the same trends. The test case was a simple two-dimensional, laminar flow of a single-phase, incompressible, Newtonian fluid around a circular cylinder at the Reynolds number of 100. A set of geometrically similar multiblock structured grids was available and boundary conditions to perform the simulations were proposed to the participants. Results from seven flow solvers were submitted, but not all of them followed exactly the proposed conditions. One set of results was obtained with adaptive grid and time refinement using triangular elements (CADYF) and another used a compressible flow solver with a dual time stepping technique and a Mach number of 0.2 (DLR-Tau). The remaining five submissions were obtained with five different incompressible flow solvers (ansyscfx 14.5, pimplefoam, refresco, saturne, starccm+ v12.06.010-R8) using implicit time integration in the proposed grids. The results obtained in this simple test case showed that iterative errors may have a significant impact on the numerical accuracy of unsteady flow simulations performed with implicit time integration. Iterative errors can be significantly larger (one to two orders of magnitude) than the residuals and/or solution changes used as convergence criteria at each time-step. The Courant number affected the magnitude of the iterative errors obtained in the proposed exercise. For the same iterative convergence criteria at each time-step, increasing the Courant number tends to increase the iterative error.
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contributor author | Eça, L. | |
contributor author | Vaz, G. | |
contributor author | Hoekstra, M. | |
contributor author | Pal, S. | |
contributor author | Muller, E. | |
contributor author | Pelletier, D. | |
contributor author | Bertinetti, A. | |
contributor author | Difonzo, R. | |
contributor author | Savoldi, L. | |
contributor author | Zanino, R. | |
contributor author | Zappatore, A. | |
contributor author | Chen, Y. | |
contributor author | Maki, K. J. | |
contributor author | Ye, H. | |
contributor author | Drofelnik, Jernej | |
contributor author | Moss, Benjamin | |
contributor author | Da Ronch, Andrea | |
date accessioned | 2022-02-04T22:17:08Z | |
date available | 2022-02-04T22:17:08Z | |
date copyright | 8/28/2020 12:00:00 AM | |
date issued | 2020 | |
identifier issn | 2377-2158 | |
identifier other | ners-20-1040.pdf | |
identifier uri | http://yetl.yabesh.ir/yetl1/handle/yetl/4275261 | |
description abstract | Two workshops were held at the ASME V&V Symposiums of 2017 and 2018 dedicated to Iterative Errors in Unsteady Flow Simulations. The focus was on the effect of iterative errors on numerical simulations performed with implicit time integration, which require the solution of a nonlinear set of equations at each time-step. The main goal of these workshops was to create awareness to the problem and to confirm that different flow solvers exhibited the same trends. The test case was a simple two-dimensional, laminar flow of a single-phase, incompressible, Newtonian fluid around a circular cylinder at the Reynolds number of 100. A set of geometrically similar multiblock structured grids was available and boundary conditions to perform the simulations were proposed to the participants. Results from seven flow solvers were submitted, but not all of them followed exactly the proposed conditions. One set of results was obtained with adaptive grid and time refinement using triangular elements (CADYF) and another used a compressible flow solver with a dual time stepping technique and a Mach number of 0.2 (DLR-Tau). The remaining five submissions were obtained with five different incompressible flow solvers (ansyscfx 14.5, pimplefoam, refresco, saturne, starccm+ v12.06.010-R8) using implicit time integration in the proposed grids. The results obtained in this simple test case showed that iterative errors may have a significant impact on the numerical accuracy of unsteady flow simulations performed with implicit time integration. Iterative errors can be significantly larger (one to two orders of magnitude) than the residuals and/or solution changes used as convergence criteria at each time-step. The Courant number affected the magnitude of the iterative errors obtained in the proposed exercise. For the same iterative convergence criteria at each time-step, increasing the Courant number tends to increase the iterative error. | |
publisher | The American Society of Mechanical Engineers (ASME) | |
title | Overview of the 2018 Workshop on Iterative Errors in Unsteady Flow Simulations | |
type | Journal Paper | |
journal volume | 5 | |
journal issue | 2 | |
journal title | Journal of Verification, Validation and Uncertainty Quantification | |
identifier doi | 10.1115/1.4047922 | |
journal fristpage | 021006-1 | |
journal lastpage | 021006-20 | |
page | 20 | |
tree | Journal of Verification, Validation and Uncertainty Quantification:;2020:;volume( 005 ):;issue: 002 | |
contenttype | Fulltext |