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Peter V. Nielsen, Aalborg University [email protected] 1
The IEA Annex 20 Two-Dimensional Benchmark Test for CFD Predictions
by
Peter V. NielsenAalborg University
Peter V. Nielsen, Aalborg University [email protected] 2
The Background for the 2D Case
Urbach (1971) Ego (1970)
Scwenke (1975) Restivo (1979)
Peter V. Nielsen, Aalborg University [email protected] 4
Publications of 2D Test Cases oncfd-benchmarks.com
7PhD - thesis
6IEA Annex 20
22005 - 2010
102000 - 2004
101995 – 1999
81990 - 1994
41989 and before
… and several more publicationsfrom e.g. internal PhD courses.
They all cover different aspectsas:• grid dependency• numerical schemes• different source codes• different turbulence models• different length scales in a
supply opening• etc…
The comparison withmeasurements can beextended by the information obtained by comparisonwith other predictions.
Peter V. Nielsen, Aalborg University [email protected] 5
Decisions to make before making a CFD Prediction
Is the flow:Laminar or turbulent?
Is the flow:Two-dimensional or three-dimensional?
Is the flow:Steady or unsteady?
Has the flow:One, two or several solutions?
Has the flow a symmetry plane?
Peter V. Nielsen, Aalborg University [email protected] 6
Decisions to make before making a CFD Prediction
Is the flow:Laminar or turbulent?
Is the flow:Two-dimensional or three-dimensional?
Is the flow:Steady or unsteady?
Has the flow:One, two or several solutions?
Has the flow a symmetry plane?
Peter V. Nielsen, Aalborg University [email protected] 7
Two-Dimensional Steady State Prediction of the Flow
Skovgaard and Nielsen (1991)
LRN k–ε model
Velocity ~ RMS
Peter V. Nielsen, Aalborg University [email protected] 8
Two-Dimensional Steady State Prediction of the Flow
Streamlines: k-ε, k-ω, BSL and SST models
k-ε model k-ω model
BSL model SST model
Peter V. Nielsen, Aalborg University [email protected] 9
Decisions to make before making a CFD Prediction
Is the flow:Laminar or turbulent?
Is the flow:Two-dimensional or three-dimensional?
Is the flow:Steady or unsteady?
Has the flow:One, two or several solutions?
Has the flow a symmetry plane?
Peter V. Nielsen, Aalborg University [email protected] 10
Three-Dimensional Steady State Prediction of the Flow
Streamlines: k-ε, k-ω and SST models
h/H = 0.056, L/H = 3.0 and W/H = 1.0
Peter V. Nielsen, Aalborg University [email protected] 11
Three-Dimensional Steady State Prediction of the Flow
Streamlines for the k-ω model
Experiments
Peter V. Nielsen, Aalborg University [email protected] 12
Decisions to make before making a CFD Prediction
Is the flow:Laminar or turbulent?
Is the flow:Two-dimensional or three-dimensional?
Is the flow:Steady or unsteady?
Has the flow:One, two or several solutions?
Has the flow a symmetry plane?
Peter V. Nielsen, Aalborg University [email protected] 13
Three-Dimensional Unsteady Flow
Davidson and Nielsen (1996)
Large Eddy Simulation (LES)
Peter V. Nielsen, Aalborg University [email protected] 14
Three-DimensionalUnsteady Flow
Davidson and Nielsen (1996)
Large eddy simulation and probability density function
Peter V. Nielsen, Aalborg University [email protected] 15
UnsteadyFlow?
Will a 3D unsteadyRANS solution givemore similar solutionsfor the differentturbulence models?
Thank you very much!