DNS 1-3 Quantification of Resolution: Difference between revisions
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==Mesh resolution== | ==Mesh resolution== | ||
The mesh resolution is quantified by obtaining a relation between the mesh characteristic length (<math>{\Delta}</math>) and the characteristics lengths, i.e., the Taylor microscale (<math>{\eta_T}</math>) and Kolmogorov length scale (<math>{\eta}</math>). The former relation is shown in [[lib:DNS_1-3_quantification_#figure1|Fig. 1]] while the latter is reported in [[lib:DNS_1-3_quantification_#figure2|Fig. 2]]. As it can be seen, both relations indicate that the resolution achieved by the present grid is at DNS level. In particular, it is commonly accepted that DNS is achieved when <math>{\Delta/\eta_T \leq 5}</math>. | |||
<div id="figure1"></div> | <div id="figure1"></div> | ||
Revision as of 08:36, 18 November 2021
Quantification of resolution
Mesh resolution
The mesh resolution is quantified by obtaining a relation between the mesh characteristic length () and the characteristics lengths, i.e., the Taylor microscale () and Kolmogorov length scale (). The former relation is shown in Fig. 1 while the latter is reported in Fig. 2. As it can be seen, both relations indicate that the resolution achieved by the present grid is at DNS level. In particular, it is commonly accepted that DNS is achieved when .
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| Figure 1: Stanford double diffuser, Alya DNS-250M DoF, relation between the mesh size and the Taylor microscale. |
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| Figure 2: Stanford double diffuser, Alya DNS-250M DoF, relation between the mesh size and the Kolmogorov length scale. |
Solution verification
The 10000 Reynolds number diffuser has been run and compared with the results with previous DNS data performed by Ohlsson et al. (2010). A P2 mesh of 250 Million of DoF. The resolution is fine enough to be at DNS level. An animation of the fluctuations of this flow can be seen in fluctuations.
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| Figure 2: Stanford double diffuser, Re=10000, preliminary validation. Average streamwise velocity, Ohlsson et al. (2010) vs preliminary data obtained with Alya. |
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| Figure 3: Stanford double diffuser, Re=10000, preliminary validation. Average streamwise velocity fluctuations, Ohlsson et al. (2010) vs preliminary data obtained with Alya. |
In Fig. 2 and Fig. 3 results are presented with reference data from Ohlsson et al. (2010). Fair agreement is observed between both calculations, proving that the approach to be used in the present proposal is an optimal strategy. Turbulent inlet was generated in a precursor domain using a long enough duct with a roughness element to trigger the laminar to turbulent transition.
Contributed by: Oriol Lehmkuhl, Arnau Miro — Barcelona Supercomputing Center (BSC)
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