High-order implicit time integration for unsteady turbulent flow simulations

2015 ◽  
Vol 112 ◽  
pp. 35-49 ◽  
Author(s):  
Peter Eliasson ◽  
Per Weinerfelt
Keyword(s):  
Turbulent Flow ◽  
Time Integration ◽  
High Order ◽  
Implicit Time ◽  
Flow Simulations ◽  
Implicit Time Integration

scholarly journals Overview of the 2018 Workshop on Iterative Errors in Unsteady Flow Simulations

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
L. Eça ◽  
G. Vaz ◽  
M. Hoekstra ◽  
S. Pal ◽  
E. Muller ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Time Integration ◽  
Implicit Time ◽  
Test Case ◽  
Convergence Criteria ◽  
Courant Number ◽  
Time Step ◽  
Flow Solver ◽  
Flow Simulations ◽  
Implicit Time Integration

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.

scholarly journals Kinetic Simulation of Collisional Magnetized Plasmas with Semi-implicit Time Integration

2018 ◽  
Vol 77 (2) ◽  
pp. 819-849 ◽  
Author(s):  
Debojyoti Ghosh ◽  
Mikhail A. Dorf ◽  
Milo R. Dorr ◽  
Jeffrey A. F. Hittinger
Keyword(s):  
Time Integration ◽  
Implicit Time ◽  
Magnetized Plasmas ◽  
Kinetic Simulation ◽  
Implicit Time Integration
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