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- BI1 - Inviscid vortex transport
- BI2 - Inviscid flow over a bump
- BI3 - Inviscid bow shock
- BL1 - Laminar Joukowski airfoil, Re=1000
- BL2 - Laminar shock-boundary layer interaction
- BL3 - Heaving & pitching airfoil
- BR1 - RANS of Joukowski airfoil
- BS1 - Taylor-Green vortex, Re=1600
- BS2 - LES channel flow Ret=590

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# Test cases

## BR1 - RANS of Joukowski airfoil

This test case is designed as a verification case of the turbulence model of the RANS equations. Participants are required to use the provided grids, as they have been demonstrated to be able to provide the optimal convergence rate in drag. A Reynolds number of 1,000,000 is employed. For an adjoint consistent discretization, the optimal convergence rate is 2P. Otherwise, the convergence rate can be expected to be P. The Joukowski airfoil is used for this test as the cusped trailing edge removes the inviscid singularity at the trailing edge. However, there is still a singularity in skin friction. The provided grids are design to cluster nodes at both the trailing edge singularity and the stagnation point in order to capture the expected order of accuracy. Hence, all participants must use the provided grids.

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## BS1 - DNS of the Taylor-Green vortex at Re=1600

This problem is aimed at testing the accuracy and the performance of high-order methods on the direct numerical simulation of a three-dimensional periodic and transitional flow defined by a simple initial condition: the Taylor-Green vortex. The computational domain is a triply periodic cubic domain, in which initially 8 vortices reside, described by an analytical formula. This flow transitions to turbulence, with the creation of small scales, followed by a decay phase similar to decaying homogeneous turbulence.

Participants are expected to perform a grid independence study on Cartesian meshes, as well as a few computations on unstructured/perturbed meshes at similar resolution as the Cartesian ones. The assessment criteria consist of the evolution of the energy dissipation rate as well as the enstrophy. Further verification is done on the basis of the kinetic energy spectrum as well as the trace of the vorticity on the periodic plane at selected time steps.

Computations need to be run on Cartesian meshes with specified equivalent resolutions 64, 128 and 256. If applicable, it is expected that participants use the unstructured and perturbed meshes provided by the test case leader to guarantee a level playing field. These will be generated in function of the interpolation (order) used by the discretization.

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## BS2 - LES of the plane channel flow at Ret=590

This test case concerns the LES of the channel flow at Reτ=590. This well-known benchmark has been intensively studied by the turbulence community. DNS and LES of the flow have been performed by numerous authors. Therefore, various quantities are available to assess the accuracy of the LES approach, such as averaged velocity and velocity fluctuations profiles and kinetic energy spectra.

Participants are expected to perform the computations for a set of structured grids which will be provided on request. Additional computations on unstructured meshes are also welcome. The assessment criteria include spatially and temporally averaged wall normal variations of the velocity and its correlations.

The participants are expected to use the meshes - structured, unstructed, and 2D extruded - provided by the test case leader in order to ensure similar grid spacing near the wall for all participants. These will be generated/provided on request as a function of the interpolation used by the discretisation method.

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## C1 - DLR F11

The DLR F-11 high lift configuration was part of the 2nd phase of the AIAA High Lift Prediction Workshop and was extensively investigated with 2nd-order state-of-the-art codes (http://hiliftpw.larc.nasa.gov/index-workshop2.html). The geometry considered for this meshing challenge is designated as configuration 4 in the original workshop and contains slat tracks and flap track fairings (see image).

The geometry is representative for a wide-body commercial aircraft with a classical three element high lift system at the wing leading and trailing edge in a landing setting. The experimental data used for the validation in the framework of HiLiftPW-2 have been measured in the atmospheric low speed wind tunnel of Airbus-Deutschland. Results of grid convergence studies using 2nd order industrial methods are available for structured and unstructured meshes for Mach number M = 0.175, Reynolds number conditions Re = 15.1 x 106 and angles of attack AoA=7°, 16° and 18.5°.

Two types of contributions are expected:

**Meshes**: participants are expected to demonstrate a methodology to generate hybrid curved meshes, including high aspect ratio extrusion boundary layers, with at least a quadratic representation of the boundary. A series of meshes following specifications by the test case organiser should be provided by March 6th.**Computations:**participants are expected to provide a single simulation for each of the three conditions. The required data follows the specification of the aforementioned workshop.

Quadratic curved hybrid mesh (3.5e6 elements: prism, pyramids and tetrahedra) by Harlan McMorris from CentaurSoft, can be provided in Gmsh or CGNS format upon request (ralf [dotcenaero] hartmanndlr [dotcenaero] de).

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## C2 - NASA Rotor 67

The NASA rotor 67 is a well-known validation test case for turbomachinery CFD codes. The aim of this challenge is to see whether fully unstructured high order simulations can be performed.

A first type of contribution concerns the

**generation of the curved (hybrid) unstructured meshes for a single passage.**The requirements are- minimally quadratic interpolation of the geometry;
- local mesh refinement following size control maps in leakage flow regions;
- curved rotationally periodic boundaries;
- extrusion curved boundary layer meshes, with an aspect ratio up to 1000 for RANS.

For meshing purposes the CAD of a single passage with and without tip gap is available in parasolid and step format. The full rotor has 22 blades.

The second type of contribution concerns the

**actual RANS/LES/WMLES computation**at two operating points, ie. near the design point and near stall. The computation will at least be taken up by the test case leader. For computational contributions, block structured curved meshes will be provided on request.- Read more about C2 - NASA Rotor 67
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